Bazett's Formula Research Articles

Association of QTc Interval and V4-S Wave With Appropriate ICD Therapy in Hypertrophic Cardiomyopathy.

BackgroundVentricular arrhythmias in patients with hypertrophic cardiomyopathy (HCM) may lead to sudden cardiac death (SCD). We aimed to investigate the relationship between electrocardiogram (ECG) indicators and the risk of appropriate implantable cardioverter-defibrillator (ICD) therapy in HCM.MethodsThe HCM patients receiving ICD implantation were enrolled consecutively. QT interval correction (QTc) was calculated using Bazett's formula. Long or deep S wave in V4 lead was defined as duration time >50 ms and/or voltage amplitude >0.6 mV. The endpoint in our study was at least one ICD appropriate therapy triggered by ventricular tachyarrhythmia (VT) or ventricular fibrillation (VF), including anti-tachyarrhythmia pacing (ATP) and electrical shock.ResultsA total of 149 patients with HCM (mean age 53 ± 14 years, male 69.8%) were studied. Appropriate ICD therapies occurred in 47 patients (31.5%) during a median follow-up of 2.9 years. Cox regression analysis showed that long or deep S wave in V4 lead [hazard ratio (HR) 1.955, 95% confidence interval (CI) 1.017–3.759, P = 0.045] and QTc interval (HR 1.014, 95% CI 1.008–1.021, P < 0.001) were independent risk factors for appropriate ICD therapy. The ROC showed that the optimal cut-off point value for the QTc interval to predict the appropriate ICD therapy was 464 ms, and the AUC was 0.658 (95% CI 0.544–0.762, P = 0.002). The AUC for S wave anomalies in V4 lead was 0.608 (95% CI 0.511–0.706, P = 0.034). We developed a new model that combined the QTc interval and S wave anomalies in V4 lead based on four patient groups. Patients with QTc ≥464 ms and long or deep V4-S wave had the highest risk of developing appropriate ICD therapy (log-rank P < 0.0001). After adding QTc interval and V4-S wave anomalies into the HCM-risk-SCD model, the prediction effect of the new model was significantly improved, and the NRI was 0.302.ConclusionsIn this HCM cohort, QTc and S wave anomalies in V4 lead were found to be significant and strong predictors of the risk of appropriate ICD therapy. Patients with QTc ≥464 ms and long or deep S wave had the highest risk. After QTc interval and V4-S wave anomalies adding to the HCM-risk-SCD model, the prediction effect is significantly improved.

Association between indices of cardiac repolarization, adiposity and metabolic syndrome. The Polish Norwegian Study (PONS)

BackgroundSeveral cardiac repolarization indices have been associated with cardiovascular disease (CVD) mortality and arrhythmia risk, but little is known about their relation to adiposity in apparently healthy individuals.Study objectiveTo compare prevalence of T‐wave inversion (TWI) and QT interval duration across levels of adiposity and metabolic health.HypothesisWe hypothesized that repolarization indices are associated with body mass index (BMI), waist circumference (WC), waist‐to‐hip ratio (WHR) and metabolic syndrome.MethodsCross‐sectional data of 10531 CVD‐free participants, age 45‐64 years. TWI was considered relevant if present in leads other than V1‐V3, on a standard 12‐lead resting ECG read by study cardiologists. QT intervals were digitally obtained by automated ECG software and were corrected for frequency (QTc, Bazett formula). Metabolic syndrome was defined according to the International Diabetes Federation criteria. We defined metabolically healthy/unhealthy normal weight (MHNW/MUHNW), metabolically healthy/unhealthy overweight (MHOW/MUHOW) and metabolically healthy/unhealthy obesity (MHO/MUO). We used logistic regression and general linear models to adjust for traditional cardiovascular risk factors and beta blockers medication.ResultsIn the overall study population (mean age [SD] 55.2 [5.3] years, 66.4% women), TWI prevalence was 2.59% and ranged from 1.4%, 2.5% to 3.9% in those with normal BMI, overweight and obesity, respectively. There was linear relation between TWI prevalence and BMI decile (p for trend &lt;0.001). Overweight and/or obesity were associated with a 1.47 (95% CI 1.02‐2.12) and 2.09 (95% CI 1.41‐3.08) higher odds of TWI respectively, after multivariable adjustment including left ventricular hypertrophy (Cornell criteria). TWI prevalence was higher for sex‐specific increased vs. normal WHR (3.16% vs. 1.78%) and WC (3.67% vs 1.90%) respectively; these increases persisted after multivariable adjustment. TWI prevalence increased from 2.12% to 3.64% in the presence of metabolic syndrome, but not statistically significant after accounting for BMI. Compared to MHNW, higher adjusted odds (OR, 95%CI) for TWI were observed for those with MHOW (1.52, 1.03‐2.24), MUHOW (1.72, 1.08‐2.77), MHO (1.98, 1.24‐3.16) and MUHO (2.78, 1.87‐4.14). QTc increased from 423.31 to 425.97 ms in the presence of sex‐specific increased WC (delta 2.67 ms, 95% CI 0.82‐4.52), but there were no statistically significant associations with BMI or metabolic syndrome after multivariable adjustments.ConclusionTWI prevalence showed a gradient with BMI and was associated with regional adiposity. Even traditionally considered metabolically healthy overweight/obesity were associated with increased TWI prevalence suggesting early repolarization abnormalities with weight gain. Potential implications: health promotion efforts in conjunction with a simple routine ECG may aid identification of individuals requiring targeted aggressive prevention interventions.

QTc prolongation in adolescents with acute alcohol intoxication

In adults, alcohol intoxication is associated with prolongation of the QT interval corrected for heart rate (QTc). The QTc is influenced by age and sex. Although alcohol intoxication is increasingly common in adolescents, there are no data on the prevalence of QTc prolongation in adolescents with alcohol intoxication. This study aimed to determine the prevalence of QTc prolongation in adolescents with alcohol intoxication and identify at-risk adolescents. In this observational study including adolescents aged 10–18 years, heart rate and QT interval were automatically assessed from an electrocardiogram (ECG) at alcohol intoxication using a validated algorithm. The QTc was calculated using both the Bazett formula (QTcB) and Fridericia formula (QTcF). If present, an ECG recorded within 1 year of the date of admission to the emergency department was obtained as a reference ECG. A total of 317 adolescents were included; 13.3% had a QTcB and 7.9% a QTcF longer than the sex- and age-specific 95th-percentile. None of the adolescents had a QTcB or QTcF > 500 ms, but 11.8% of the adolescents with a reference ECG had a QTcB prolongation of > 60 ms, while no adolescents had a QTcF prolongation of > 60 ms. QTc prolongation was mainly attributable to an increase in heart rate rather than QT prolongation, which underlies the differences between QTcB and QTcF. Male sex and hypokalaemia increased the likelihood of QTc prolongation.Conclusion: QTc prolongation was seen in approximately 10% of the adolescents presenting with alcohol intoxication, and although no ventricular arrhythmias were observed in this cohort, QTc prolongation increases the potential for malignant QT-related arrhythmias. Clinicians must be aware of the possibility of QTc prolongation during alcohol intoxication and make an effort to obtain an ECG at presentation, measure the QT interval, and give an adequate assessment of the findings. We advocate admitting adolescents with alcohol intoxication and QTc prolongation. During hospital admission, we recommend limiting exposure to QTc-prolonging medication, increasing potassium levels to a high-normal range (4.5–5.0 mmol/L) and obtaining a reference ECG at discharge.What is Known:• One out of five deaths in adolescents is alcohol-related. Alcohol intoxication has been related to cardiac arrhythmias and sudden cardiac death.•In adults, alcohol intoxication is associated with QTc prolongation.What is New:•Approximately 10% of the adolescents with alcohol intoxication had a QTc longer than the age- and sexspecific cut-off. In contrast to adults, in adolescents with alcohol intoxication, QTc prolongation is attributable to an increase in heart rate, rather than a prolongation of the QT interval.•Especially males and adolescents with hypokalaemia are at risk of QTc prolongation.

Frequency of QTc Interval Prolongation in Children and Adults with Williams Syndrome.

QTc prolongation (≥ 460ms), according to Bazett formula (QTcB), has been identified to be increased in Williams syndrome (WS) and suggested as a potential cause of increased risk of sudden cardiac death. The Bazett formula tends to overestimate QTc in higher heart rates. We performed a retrospective chart review of WS patients with ≥ 1 electrocardiogram (EKG) with sinus rhythm, no evidence of bundle branch blocks, and measurable intervals. A total of 280 EKGs from 147 patients with WS were analyzed and 123 EKGs from 123 controls. The QTc was calculated using Bazett formula. The average QTcB for individuals with WS and controls was 444 ± 24ms and 417 ± 26ms, respectively (p < 0.001). In our WS cohort 34.4% had at least 1 EKG with a QTcB ≥ 460ms. The mean heart rate (HR) from patients with WS was significantly higher than controls (96bpm vs 76bpm, p < 0.001). Linear regression showed that HR contributed 27% to QTcB prolongation in the patients with WS. Patients with WS have a mean QTcB in the normal range but higher than controls, and a higher than expected frequency of QTc ≥ 460ms compared to the general population. HR is also higher in WS and contributes modestly to the WS QTcB prolongation. Future studies are needed to assess if these findings contribute risk to sudden cardiac death but in the interim we recommend routine EKG testing, especially when starting QTc prolonging medications.

CPNP 2022 Annual Meeting Poster Abstracts

CPNP 2022 Annual Meeting Poster Abstracts

Definition of the dependence of QTc interval prolongation on glycemic control in patients with type 2 diabetes mellitus

The aim of the study: to assess the impact of glycemic variability on the duration of QTc interval in patients with diabetes mellitus type 2. 68 patients with type 2 diabetes mellitus (DM) and glycosylated hemoglobin (HbA1c) level ≤10% were examined. Of them – 37 (54.4%) men and 31 (45.6%) women. The average age – 46.0 (43.0; 54.0) years, the duration of DM type 2 – 7.0 (5.0; 9.0) years. Patients were divided into 2 groups according to HbA1c level: group 1 (n=31) with HbA1c &lt;7% and group 2 (n=37) with HbA1c ≥7%. The control group consisted of 10 practically healthy people, compared by gender and age. The duration of the QTc interval was calculated automatically by Bazett's formula during 24-hour Holter electrocardiogram (ECG) recordings. Additionally, the percentage of cases of exceeding the QTc threshold over 450 ms (QTc&gt;450) was also calculated. Simultaneously with 24-hour Holter monitoring, the continuous glucose monitoring was performed, using iPro2 system (Medtronic MiniMed, USA). The maximum value of glycemia (Gmax), the minimum value of glycemia (Gmin), as well as indicators of glycemia variability (GV) were analyzed: standard deviation of mean glycemia (SD) and glycemia range (GR). The duration of daily QTc and the value of QTc &gt;450 in patients with type 2 DM were significantly greater compared with the control group (p&lt;0.05) and did not depend on the HbA1c level. In type 2 DM patients without recorded hypoglycemic episodes, the characteristics of QTc did not differ from the results of the control group (p&gt;0.05). At the time of the hypoglycemic episode, the QTc duration in patients with type 2 DM significantly increased compared with the average daily value of QTc in the same patients – 487 (466; 519.5) ms against 436.5 (431; 452) ms (p&lt;0.001). A strong correlation between QTc duration and the presence of hypoglycemia was determined (rs=0.78; p=0.023). QTc duration also correlated with GR (rs=0.23; p=0.016) and SD (rs=0.21; p=0.021). Therefore, it was found that in patients with type 2 diabetes, the prolongation of QTc duration is associated with high glycemic fluctuations and hypoglycemia (p&lt;0.05) regardless of the HbA1c level.

Effects of azithromycin on ventricular repolarization in children with COVID-19

IntroductionAzithromycin is used to treat pediatric COVID-19 patients. It can also prolong the QT interval in adults. This study assessed the effects of azithromycin on ventricular repolarization in children with COVID-19. MethodThe study prospectively enrolled children with COVID-19 who received azithromycin between July and August 2020. An electrocardiogram was performed before, one, three, and five days post-treatment. Using ImageJ®, the following parameters were measured: QT max, QT min, Tp-e max, and Tp-e min. The parameters QTc max, QTc min, Tp-ec max, Tp-ec min, QTcd, Tp-ecd, and the QTc/Tp-ec ratio were calculated using Bazett's formula. ResultsThe study included 105 pediatric patients (mean age 9.8±5.3 years). The pretreatment heart rate was higher than after treatment (before 92 [79–108]/min vs. Day 1 82 [69–108)]/min vs. Day 3 80 [68–92.2]/min vs. Day 5 81 [70–92]/min; p=0.05). ConclusionAzithromycin does not affect the ventricular repolarization parameters on ECG in pediatric COVID-19 cases.

Corrected QT interval and GRACE score relationship in patients with non-ST segment elevation myocardial infarction

The Global Registry of Acute Coronary Events (GRACE) prediction model stratifies patients with non-ST-segment elevation myocardial infarction (NSTEMI). Corrected QT interval (QTc) is not considered in this model. To evaluate the relationship between the QTc interval and the GRACE score in patients with NSTEMI. An observational, retrospective study was carried between 2016 and 2019. We included patients with diagnosis of NSTEMI, QTc intervals were calculated with Bazett's formula, and they were classified into 2 groups: a normal QTc interval (<440 ms) and prolonged (≥440 ms). According to the GRACE score they were classified in three ranges: low risk (≤109 points), intermedium (110 - 139 points) and high (≥140 points), we determined if there were a correlation between QTc interval and the GRACE score. A total of 940 patients with a diagnosis of NSTEMI were admitted in our institution, 634 met the inclusion criteria, there were 390 patients with normal QTc interval and 244 with a prolonged QTc interval. Patients with prolonged QTc were older (65.5 vs 61, p=0.001) with a lower proportion of males (71.7% vs 82.8%, p=0.001). An association was found between the GRACE score and the QTC interval, subjects with a normal QTc had a greater proportion of low and intermediate risk than those with a prolonged QTc (p=0.001). Conclusions. In NSTEMI patients, a normal QTc interval (<440 ms) is associated with a GRACE risk score of low or intermediate risk.

Impact of Heart Rate and Rhythm on Corrected QT Interval During Paroxysmal Atrial Fibrillation

Current knowledge on the dynamic changes of corrected QT (QTc) before, during, and after an atrial fibrillation (AF) episode is limited. It remains controversial which of the presently available formulas performs the best in calculating QTc during AF. This study was designed to explore whether an AF attack would affect QTc and to determine the performance of 6 available formulas in correcting QT before, during, and after AF. A total of 101 patients with Holter-documented paroxysmal AF were enrolled. QT interval before, during, and after AF was measured and corrected to heart rate (HR) by using Bazett, Fridericia, Framingham, Hodges, Dmitrienko, and RTHa formulas. In 40 patients, QTc under AF was compared with under sinus rhythm (SR) with identical HR. Although QT was significantly longer before AF and after AF compared with during AF; there was no difference in QTc between SR and AF with identical HR regardless of the formulas used. QTc calculated by the Framingham formula showed excellent homogeneity with a mean delta difference of -0.2 ± 41.6ms (before AF vs AF) and -6.6 ± 35.4ms (after AF vs AF), respectively. QTc corrected by the Bazett formula (before AF vs AF -38.7 ± 52.3ms; after AF vs AF -42.6 ± 46.9ms) yielded significant heterogeneity among the 3 time points. In conclusion, AF does not influence QTc. The Framingham formula accurately corrects QT without being affected by the AF episode. The Bazett formula significantly overestimated QTc during AF.

Measuring the QT/QTc Interval in the Presence of Wide QRS Complexes

Scenario: The electrocardiographic (ECG) rhythm strip below (leads V1 and II) is from a 68-year-old woman with pneumonia who was admitted to the step-down unit from a long-term care facility. Vital signs upon arrival included blood pressure, 107/61 mm Hg; body temperature, 98.9 °F (37.2 °C); heart rate, 68/min; respiratory rate, 21/min; and oxygen saturation (SpO2), 96% on 4 L of oxygen. The attending physician ordered intravenous levofloxacin based on culture of a blood sample collected in the emergency department. Per unit policy, because intravenous levofloxacin is known to prolong the QT/QTc, the nurse must measure and document the QT/QTc before starting the medication in order to determine whether QT/QTc prolongation occurs after administration. How should the QT/QTc be measured in this patient?Sinus rhythm, right bundle branch block (RBBB), possible prior anteroseptal myocardial infarction (MI), and old inferior wall MI.When measuring the QT/QTc in a patient with BBB (RBBB, in this case), because ventricular depolarization is delayed (ie, left to right ventricle), the QT/QTc is prolonged (compare “normal QRS” above). Therefore, the QT/QTc measured in patients with BBB (right or left) has to be adjusted to avoid overestimation. The Bogossian method can be used in patients with BBB, where the modified QT (QTM) is calculated using QT – (QRS/2).1 The QTM is then used to calculate the QTc to account for heart rate using the Bazett formula, or QTM/RR. In this example, QT/QTc would be calculated as follows: QTM = 440 – (160/2) = 360 milliseconds, and RR is 800 milliseconds or 0.8 seconds, so QTc=0.36/0.8=0.402 seconds or 402 milliseconds, which is within the normal range. In comparison, whereas the QT interval is within normal range without using the Bogossian formula, when corrected for heart rate the QTc was prolonged (ie, QTc without Bogossian correction = 0.44/0.8 = 0.492 seconds = 492 milliseconds); hence, adjusting QTc to account for the RBBB in this patient was important.In patients with RBBB, while conduction down the right bundle branch is “blocked,” an initial r wave should be present in lead V1, resulting in the classic rsR’ pattern associated with RBBB (see normal QRS above). However, in patients with a prior septal wall MI, the initial r wave will not be present because depolarization is disrupted in this myocardial region, as is seen in this example. Acute ischemia may be present when examining lead V1 because one would expect the ST segment to be sloping downward and not to be isoelectric with the PR interval. A Q wave is also seen in lead II, which is ~40 milliseconds, suggesting that this patient may also have a prior inferior wall MI, although this feature may be associated with the RBBB.Based on the QT/QTc calculated using the Bogossian correction and Bazett formulas, the antibiotic can be administered to this patient safely. However, QT/QTc should be measured every 8 to 12 hours as it can become prolonged after antibiotic administration. Because of the ECG waveform changes suggestive of prior septal and inferior wall MI and possible acute ischemia, a 12-lead ECG should be obtained to rule out these conditions. In this patient, prior inferior wall (abnormal Q wave in leads III and aVF) and septal wall (missing r wave in lead V2) MI was confirmed. The 12-lead ECG also showed possible acute myocardial ischemia in the other precordial leads; hence, a cardiac workup (ie, cardiac troponin blood test, serial ECGs, and echocardiogram) was ordered. The QT/QTc measured in lead V1 of the 12-lead ECG did not differ from the above measurement. Careful continuous ECG monitoring for ventricular arrhythmias (ie, torsades de pointes, ventricular tachycardia/fibrillation) is paramount in this patient because of the possibility of QT/QTc prolongation and ECG changes suggestive of acute ischemia. Ultimately, this patient was treated for both pneumonia and myocardial ischemia. She did not have QT/QTc prolongation or ventricular arrhythmias and was discharged back to the long-term care facility.

Prognostic Value of Long Corrected QT Interval on Electrocardiogram in Acute Organophosphate Poisoning: A Cohort Study

Introduction: According to data available from National Poison Information Centre India, suicidal poisoning with household agents (organophosphates, carbamates etc.) is the most common modality of poisoning. There are reports suggesting relationship between prolonged corrected QT interval and the severity of Organophosphate (OP) poisoning. Corrected QT (QTc) interval is measured in 12 lead electrocardiograms taken on admission. Aim: To assess prognosis of acute organophosphate poisoning patients by studying association of corrected QT interval with its complications and mortality. Materials and Methods: The cohort study was conducted at Medicine Department of Medical College, Baroda and Sir Sayaji General Hospital, Vadodara, Gujarat, India, from December 2017 to November 2018. The study included 60 patients with a history of OP poisoning. The QTc interval in electrocardiogram was determined by using the Bazett formula. Prognostic importance of QTc interval was assessed by correlating it with Paradeniya Organophosphorus Poisoning Scale score, hospital stay, atropine requirement, requirement of ventilatory support and mortality. Data was analysed by using descriptive statistics and Chi-square test. Results: The organophosphate poisoning was seen more in younger age group, between 18-29 years (68.4%). The QTc prolongation was seen in 12, 80% of patients in moderate grade of Paradeniya Organophosphorus Poisoning Scale and in 9 (20%) patients among mild grade of Paradeniya Organophosphorus Poisoning Scale (p-value=0.0001). Amongst patients who needed hospital stay for more than 7 days, QTc prolongation was seen in 43% of patients, and in patients who needed hospital stay for less than 7 days QTc prolongation was seen in 9% of patients (p-value=0.0223). Statistically significant association was seen between atropine ampule requirement and QTc prolongation. Total 29 (48.3%) patients developed respiratory depression, and amongst them 19 (65.5%) had QTc prongation (p-value &lt;0.0001). Thirteen (22%) patients died and amongst them 12 (92.31%) had QTc prolngation. In those who survived (47,78%) only 9 (19.15%) had QTc prolongation (p-value &lt;0.0001). Conclusion: Prolonged QTc interval in electrocardiogram is a good prognostic indicator in patients with organophosphorus poisoning. Early identification of prolonged QTc interval and subsequent timely shifting of patients to Intensive Care Unit (ICU) and subsequent intensive management in a patient of OP poisoning would be of profound value at any level of health care setting for favourable outcomes.

Estimation of cardiac QTc intervals in people prescribed antipsychotics: a comparison of correction factors.

Background:A prolonged electrocardiogram (ECG) QT interval is associated with cardiac events and increased mortality. Antipsychotics can prolong the QT interval. The QT interval requires correction (QTc) for heart rate using a formula or QT-nomogram. The QT and QTc can be calculated automatically by the ECG machine or manually; however, machine-measured QT(c) intervals may be inaccurate.Objective:We aimed to investigate the mean QTc and proportion of prolonged QTc intervals in people taking antipsychotic medicines.Methods:We conducted an observational retrospective chart review and data analysis of all consecutive patients taking antipsychotics, with an ECG record, admitted to the psychiatric unit of a large tertiary hospital in Brisbane, Australia, between 1 January 2017 and 30 January 2019. We investigated the mean QTc of people taking antipsychotics to determine differences using (a) machine versus manual QT interval measurement and (b) QTc correction formulae (Bazett, Fridericia, Framingham, Hodges and Rautaharju) and the QT-nomogram. We also determined the number of people with a prolonged QTc using different methods and compared rates of prolonged QTc with antipsychotic monotherapy and polypharmacy.Results:Of 920 included people, the mean (±SD) machine-measured, Bazett-corrected QT interval (recorded from the ECG) was 435 ms (±27), significantly longer (p < 0.001) than the mean manually measured corrected QT intervals with Fridericia 394 ms (±24), Framingham 395 ms (±22), Hodges 398 ms (±22) and Rautaharju 400 ms (±24) formulae. There were significantly more people with a prolonged QTc using machine-measured QT and the Bazett formula (12.0%, 110/920) when compared with manually measured QT and the Fridericia formula (2.2%, 20/920) or QT-nomogram (0.7%, 6/920). Rates of QTc prolongation did not differ between people taking antipsychotic polypharmacy compared with monotherapy.Conclusion:Machine-measured QTc using the Bazett formula overestimates the QTc interval length and number of people with a prolonged QTc, compared with other formulae and the QT-nomogram. We recommend manually measuring the QT and correcting with the Fridericia formula or QT-nomogram prior to modifying antipsychotic therapies.

Physiological QT Interval Changes in Early Infancy Using Post-Menstrual and Post-Natal Age Calculation for Electrocardiogram Long QT Interval Screening in Taiwan.

Prolongation of the QT interval is associated with the risk of sudden infant death syndrome. QT interval differs depending on age at the time of screening. Screening protocols have yet to be established for Taiwanese patients. To construct QT interval reference values during early infancy, to investigate whether QT interval change differs according to age calculation methods, and to identify an optimal QT correction method and associated infant factors. Electrocardiographic readings and QT intervals were recorded cross-sectionally in 595 healthy infants and screened prospectively for long QT interval. Corrected QT intervals with Bazett's (QTc-B) and Fridericia's (QTc-F) formulas were compared by post-natal and post-menstrual screening age, sex, body mass index (BMI), heart rate (HR), birth and family history. QTc-B and QTc-F decreased in the second month (31-60 days), and peaked in the third month (61-90 days). QT interval length was similar between post-menstrual and post-natal ages for QTc-B. Simple linear regression showed that post-menstrual age, post-natal age, HR and BMI were associated with QTc-F, while only sex and HR were associated with QTc-B. Although both QTc-B and QTc-F were significantly associated with HR, QTc-B was less affected by HR than QTc-F (β = -0.1, p < 0.05 for QTc-B vs. β = -0.3, p < 0.001 for QTc-F). Female infants tended to have slightly longer QTc intervals. QT interval in early infancy changed physiologically, peaking in the third month. The rate of QT change was not affected by different age correction methods. QTc-B was less affected by age, BMI and HR, although differences in sex should be noted.

Correlation between short-term heart rate variability and QT-Interval with left ventricular systolic function in patients with stable Coronary Artery Disease (CAD): a cross-sectional study

Background: The ischemic process in stable Coronary Artery Disease (CAD) causes cardiac remodeling and dysfunction, signaling the progress towards irreversible heart failure. Early identification for the presence of Left ventricular (LV) remodeling and dysfunction is important. Several methods can be used to assess LV dysfunction using echocardiography, including peak Global Longitudinal Strain (GLS) and ejection fraction measurements. Short-term Heart Rate Variability (HRV) and QT interval are considered practical parameters in electrocardiography identifying LV dysfunction. This study aimed to determine the relationship between short-term HRV and QT interval with LV systolic function in stable angina pectoris patients.Methods: This cross-sectional study was conducted in Prof. Dr. R. D. Kandou Hospital, Manado, from March to September 2021. All study subjects who met the inclusion criteria underwent a clinical history and further examinations, including electrocardiography, laboratory, and echocardiography examinations. The relationship of HRV variables and QT interval with LV systolic function were analyzed using Pearson correlation and linear regression models by SPSS version 21 for Windows.Results: A total of 33 subjects were included with a mean age of 62.3±8.9 years. Non-parametric correlation analysis between HRV variables and left ventricular systolic function showed no significant correlation. There was a significant correlation between QTc interval by Fridericia and LV peak GLS, but not with ejection fraction (r=0.426; p=0.013). The univariate regression analysis showed a relationship between QTc interval by Bazett and Fridericia with peak GLS (Bazett B=0.036; ?=0.35; R2=0.122; p=0.046; Fridericia B=0.052; ?=0.426; R2=0.181; p=0.013).Conclusion: There was a weak and moderate positive correlation between the QTc interval by Bazett and Fridericia formula with left ventricular systolic function. There was no statistically significant correlation between the short-term HRV variable and left ventricular systolic function.

Sonographic Assessment of the Effects of Mechanical Ventilation on Carotid Flow Time and Volume.

BackgroundCorrected carotid flow time (CFTc) and carotid blood flow (CBF) are sonographic measurements used to assess fluid responsiveness in hypotension. We investigated the impacts of mechanical ventilation on CFTc and CBF.Materials and methodsNormotensive patients undergoing cardiac surgery were prospectively enrolled. Carotid ultrasound (US) was performed pre and post-intubation. Post-intubation measurements took place after the initiation of mechanical ventilation. To measure CFTc and CBF, a sagittal carotid view was obtained with pulse wave-Doppler (maximum angle 60°). CFTc was calculated with the Bazett formula (CFTc = systolic time/√cycle time). CBF was calculated using CBF (mL/min) = area (cm 2 ) x time average mean velocity (TAMEAN) (cm/sec) x 60 (sec/min). The maximum carotid diameter was measured at the level of the thyroid.ResultsTwenty patients were enrolled. Mean CFTc pre-intubation was 328 ms (SD 43.9 ms) compared to CFTc post-intubation 336 ms (SD 36 ms). There was no significant difference between pre and post-intubation CFTc (mean differences=-0.008; t(19)=-0.71, p=.49). Mean CBF pre-intubation was 487 mL/min (SD 176 mL/min) compared to CBF post-intubation 447 mL/min (SD 187 mL/min). There was no significant difference between pre and post-intubation CBF (mean differences= 40; t(19)=1.24, p=.23).ConclusionsIn this study of normotensive patients, there were no detected differences in CFTc or CBF pre and post-intubation with mechanical ventilation.

Effects of hydroxychloroquine and its metabolites in patients with connective tissue diseases.

Hydroxychloroquine has attracted attention in the treatment of COVID-19. Many conflicting findings have been reported regarding the efficacy and safety of this drug, which has been used safely in the rheumatological diseases for years. However, these studies lacked measurement methods that allow accurate assessment of hydroxychloroquine and its metabolite levels. The aim of this study was to measure hydroxychloroquine and its metabolite levels in whole blood samples of patients with rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), Sjogren’s syndrome (SS) and scleroderma (Scl) by a robust, simple and accurate validated tandem mass spectrometric method, and to investigate the relationship between these levels with drug-related adverse effects and disease activity scores. The validated LC–MS/MS method was applied to measure blood hydroxychloroquine and its metabolite levels of patients with RA, SLE, SS, Scl. Various haematological and biochemical parameters were measured with Beckman-Coulter AU 5800 and Beckman Coulter LH 780 analyzers, respectively. QTc intervals were calculated with Bazett’s formula, and the patients were followed up by clinicians in terms of clinical findings and adverse effects. Hydroxychloroquine levels of patients were similar to previous studies. There was a negative correlation between disease activity scores and hydroxychloroquine levels, while the highest correlation was between QTc interval, creatinine and GFR levels with desethylchloroquine. Bidetylchloroquine had the highest correlation with RBC count and liver function tests. Our findings showed that hydroxychloroquine and its metabolite levels were associated with disease activity scores, renal, hepatic function, QTc prolongation, and hematological parameters.

QTc interval on 24-hour holter monitor: To trust or not to trust?

IntroductionQT interval represents the ventricular depolarization and repolarization. Its accurate measurement is critical since prolonged QT can lead to sudden cardiac death. QT is affected by heart rate and is corrected to QTc via several formulae. QTc is commonly calculated on the ECG and not the 24‐h Holter.Methods100 patients presenting to our institution were evaluated by an ECG followed by a 24‐h Holter. QTc measurement on both platforms using Bazett and Fridericia formulae was recorded and compared.ResultsMean age was 14.09 years, with the majority being males. Mean heart rate was 125.87. In the ECG, the mean QTc interval via the Bazett formula was 0.40 s compared with 0.38 s using the Fridericia formula. The mean corrected QT via the Bazett formula was 0.45, 0.39, and 0.42 s for the shortest RR, the longest RR, and the average RR, respectively. In contrast to the Fridericia formula, the corrected QT interval was 0.40, 0.39, and 0.40 s for the shortest RR, the longest RR, and the average RR, respectively. Using the Bazett formula, the highest specificity was reached during the longest RR interval (92.2%), while the highest sensitivity was recorded during the shortest RR interval (40%). As for the Fridericiaformula, sensitivity always reached 0%, while the highest specificity was reached during the average RR interval.ConclusionQTc measured during Holter ECG reached a high specificity regardless of RR interval using the Fridericia and during the longest and the average RR interval for the Bazett formula. The consistently low sensitivity reveals that Holter ECG should not be used to rule out prolonged QT.

Emotional and cardiovascular health: the impact of depression on cardiac autonomic activity

Abstract Background The coexistence of depression and cardiovascular diseases is frequently accompanied by an increased risk of adverse outcomes. QTc, an indicator of ventricular depolarization and cardiac autonomic activity, has been proposed as a biomarker of this interplay. Purpose We aimed to investigate the possible association of depression with QTc interval. Methods Assessment of depressive symptoms was performed in 1637 participants of the cross-sectional Corinthia study with the Zung self-rating depression scale in those younger than 65 years of age (Group 1) and with the geriatric depression scale in elderly individuals (&amp;gt;65 years, Group 2). Moreover, electrocardiogram was performed and measurement of the QT interval was derived after correction for heart rate (QTc) using the Bazett's formula. Abnormal QTc was present when QTc duration exceeded 440 ms. Results Group 1 individuals classified as having depression had longer QTc duration (No depression: 389.3±27.0 ms vs. Depression: 401.1±32.9 ms, p&amp;lt;0.001) and percentage of abnormal QTc (No depression: 2.0% vs. Depression: 10.8%, p=0.001) (Figure 1, Panels A and B). Elderly individuals had similar values of QTc (No depression: 409.9±29.6 ms vs. Depression: 405.2±46.4 ms, p=0.37) and percentage of abnormal QTc (No depression: 13.2% vs. Depression: 12.3%, p=0.78) irrespective of depression status (Figure 1, Panels C and D). The presence of depression in Group 1 subjects was associated with an increased QTc- by 10.8 ms and with an approximately 7-fold higher prevalence of abnormal QTc duration, even after adjustment for confounders (). Such finding was not detected in elderly individuals (Figure 1, Panel F). Conclusion Depression might adversely affect ventricular repolarization especially in middle-aged subjects. These findings highlight the interrelationship between emotional and cardiovascular health and the role of depression as a cardiovascular risk factor. Funding Acknowledgement Type of funding sources: None. Figure 1

Temporary prolongation of corrected QT interval after cardioneuroablation for functional bradyarrhythmias

Abstract Background There are controversial reports on QT interval response to ganglionic plexi ablation that are selectively targeted during cardioneuroablation (CNA) or occurs as collateral lesion during left atrial ablation procedures. Both shortening or prolongation of the heart-rate corrected QT interval (QTc) with therapeutic or safety implications were described. Purpose In this retrospective study, we investigated longitudinal changes of QTc after CNA. Methods The study included 108 patients (age: 39±12 years, 60% males) who underwent biatrial cardioneuroablation (radiofrequency time: 15.5±6.7 min) for symptomatic functional bradyarrhythmias. Surface ECG examinations were performed on the day before the CNA (N=108), 1 hour after the CNA (N=106), on the 1st post-ablation day (N=50), at the 3-month (N=99), and 1-year (N=63) follow-up visits. Automated measurements of QT interval were employed for the analysis. Four formulas (Bazett, Framingham, Fridericia, and Hodges) were used for the correction of QT interval to instant heart rate. Results QTc significantly prolonged immediately after the CNA with rapid return to baseline values (Figure and Table). This was particularly valid for QT correction by Framingham formula (and similarly for Fridericia and Hodges formulas). The QTc by Bazett formula, which is known to overestimate QT at higher heart rates, returned to baseline more slowly and incompletely. Several mechanisms may contribute to observed QTc dynamics: (1) direct effect of autonomic denervation with recovery phenomenon; (2) QT hysteresis with an extremely long time constant; or (3) artifact due to suboptimum QT correction to a substantial change of heart rate. Conclusions The study suggests that CNA produces acute prolongation of QTc interval with rapid decay and virtual normalization in 3 months. CNA in otherwise healthy subjects is not likely associated with substantial long-term risk of long-QT-associated arrhythmias. In the same way, we cannot confirm earlier observations of clinically significant QTc shortening effect of ganglionated plexi ablation. Funding Acknowledgement Type of funding sources: None. Figure 1Table 1

QTc interval in Acute Severe Asthma

Abstract Background Prolonged QTc interval in children may be congenital or acquired. It could be fatal if it induces tachyarrhythmias and cardiac arrest. Objectives This work studied the QTc interval in acute asthma attacks and its relation to the severity of the attack and the bronchodilators used. Patients and Methods This is a descriptive prospective study of 30 children with moderate and severe asthma. Patients were divided according to GINA guidelines 2016: Group 1:10 patients with moderate acute attack, Group Il: 20 patients with severe acute attack. 12 lead ECG was done before start of medication, then repeated daily till discharge. QTc interval measured in lead V5 using Bazett Formula was considered prolonged if &amp;gt; 445msec. Results Our study showed that 4 patients (13%) developed prolonged QTc interval; 3 (75%) had severe attack and one (25%) had moderate attack. QTc interval increased with number of bronchodilators used, but not reaching statistical significance. On day2, QTc was 340—435msec in patients on 2 medications and 350—460msec in patients on 3 medications. However, on 3rd day QTc interval was between 348-410msec,346—420msec,350—446msec in patients having 1, 2, 3 medications respectively. Also, there was no relation between theophylline and prolonged QTc interval. Conclusion Prolonged QTc interval can occur in 13% of children with moderate and severe asthma. QTc interval increased with number of bronchodilators used yet not reaching statistical significance. Bronchodilators must be used judiciously since they might be potentially arrhythmogenic drugs that induce fatal arrhythmia .