T-wave Polarity Research Articles

Association of Positive TwaVR/STaVR ECG Changes with Adverse Outcomes in Heart Failure Patients with Reduced Ejection Fraction Undergoing CABG in Turkey: A Retrospective Study.

Positive T-wave polarity in the augmented vector right lead (Tw-aVR) and ST-segment deviation in the augmented vector right lead (STaVR) have been identified as potential predictors of adverse outcomes in various cardiac conditions. The aim of the study was to examine the effect of positive Tw-aVR and STaVR on in-hospital mortality after coronary artery bypass grafting (CABG) surgery in patients with heart failure with reduced ejection fraction (HFrEF). A five-year retrospective study was conducted on 250 HFrEF patients who underwent CABG at a tertiary care hospital between January 2018 and December 2022. The primary outcome was in-hospital mortality, and the main exposures were positive Tw-aVR and STaVR on preoperative electrocardiograms. Logistic regression models were used to assess the factors associated with in-hospital mortality. Two hundred and fifty patients with a mean age of 67.4 ± 8.1 years were studied. Males constituted 68% of the participants. Among the participants, 60 (24%) had positive Tw-aVR, and 96 (38.4%) had STaVR. The overall in-hospital mortality rate was 7.6%, and patients with positive Tw-aVR and STaVR had significantly higher mortality rates than those without (odds ratio: 3.62 and 2.87, respectively, P < 0.01). These associations remained significant even after controlling for potential confounders such as age (adjusted odds ratio [AOR]: 1.11; 95% confidence interval [CI]: 1.03-1.20; P = 0.008), sex (AOR: 0.82; 95% CI: 0.31-2.18; P = 0.684), diabetes mellitus (AOR: 2.12; 95% CI: 0.88-5.12; P = 0.091), and chronic kidney disease (AOR: 1.79; 95% CI: 0.75-4.27; P = 0.194). Positive Tw-aVR and STaVR were found to be associated with in-hospital mortality in HFrEF patients after CABG. These findings suggest that identifying patients with positive Tw-aVR and STaVR may help identify those at higher risk of adverse outcomes and facilitate closer monitoring and more aggressive interventions.

Catecholamines are key modulators of ventricular repolarization patterns in the ball python (Python regius).

Ectothermic vertebrates experience daily changes in body temperature, and anecdotal observations suggest these changes affect ventricular repolarization such that the T-wave in the ECG changes polarity. Mammals, in contrast, can maintain stable body temperatures, and their ventricular repolarization is strongly modulated by changes in heart rate and by sympathetic nervous system activity. The aim of this study was to assess the role of body temperature, heart rate, and circulating catecholamines on local repolarization gradients in the ectothermic ball python (Python regius). We recorded body-surface electrocardiograms and performed open-chest high-resolution epicardial mapping while increasing body temperature in five pythons, in all of which there was a change in T-wave polarity. However, the vector of repolarization differed between individuals, and only a subset of leads revealed T-wave polarity change. RNA sequencing revealed regional differences related to adrenergic signaling. In one denervated and Ringer's solution-perfused heart, heating and elevated heart rates did not induce change in T-wave polarity, whereas noradrenaline did. Accordingly, electrocardiograms in eight awake pythons receiving intra-arterial infusion of the β-adrenergic receptor agonists adrenaline and isoproterenol revealed T-wave inversion in most individuals. Conversely, blocking the β-adrenergic receptors using propranolol prevented T-wave change during heating. Our findings indicate that changes in ventricular repolarization in ball pythons are caused by increased tone of the sympathetic nervous system, not by changes in temperature. Therefore, ventricular repolarization in both pythons and mammals is modulated by evolutionary conserved mechanisms involving catecholaminergic stimulation.

Science, Medicine, and the Anesthesiologist

Science, Medicine, and the Anesthesiologist

Prone and Supine 12-Lead ECGComparisons: Implications for Cardiac Assessment During Prone Ventilationfor COVID-19.

ObjectivesThis study sought to describe expected changes in a mirror-image prone electrocardiogram (ECG) compared with normal supine, including a range of cardiac conditions.BackgroundUnwell COVID-19 patients are at risk of cardiac complications. Prone ventilation is recommended but poses practical challenges to acquisition of a 12-lead ECG. The effects of prone positioning on the ECG remain unknown.Methods100 patients each underwent 3 ECGs: standard supine front (SF); prone position with precordial leads attached to front (PF); and prone with precordial leads attached to back in a mirror image to front (PB).ResultsProne positioning was associated with QTc prolongation (PF 437 ± 32 ms vs. SF 432 ± 31 ms; p < 0.01; PB 436 ± 34 ms vs. SF 432 ± 31 ms; p = 0.02). In leads V1 to V3 on PB ECG, a qR morphology was present in 90% and changes in T-wave polarity in 84%. In patients with anterior ischemia, ST-segment changes in V1 to V3 on supine ECG were no longer visible on PB in 100% and replaced by an R-wave in V1. Bundle branch block (BBB) remained detectable in 100% on PB, with left BBB appearing as right BBB on PB in 71% and QRS narrowing with qR in V1 for right BBB. ST-segment/T-wave changes in limb leads and arrhythmia detection were largely unaffected in PB.ConclusionsAs expected, the PB ECG is unreliable for the detection of anterior myocardial injury but remains useful for ST-segment/T-wave abnormalities in limb leads, BBB detection, and rhythm monitoring. The prone ECG is a useful screening tool with diagnostic utility in COVID-19 patients who require prone ventilation.

CARDIAC EXAMINATIONS OF ANESTHETIZED STELLER SEA LIONS (EUMETOPIAS JUBATUS), NORTHERN FUR SEALS (CALLORHINUS URSINUS), AND A WALRUS (ODOBENUS ROSMARUS).

Pinniped hearts have been well described via dissection, but in vivo measurements of cardiac structure, function, and electrophysiology are lacking. Electrocardiograms (ECGs) were recorded under anesthesia from eight Steller sea lions (Eumetopias jubatus), five northern fur seals (Callorhinus ursinus), and one walrus (Odobenus rosmarus) to investigate cardiac electrophysiology in pinnipeds. In addition, echocardiograms were performed on all eight anesthetized Steller sea lions to evaluate in vivo cardiac structure and function. Measured and calculated ECG parameters included P-wave, PQ, QRS, and QT interval durations, P-, R-, and T-wave amplitudes, P- and T-wave polarities, and the mean electrical axis (MEA). Measured and calculated echocardiographic parameters included left ventricular internal diameter, interventricular septum thickness, and left ventricular posterior wall thickness in systole and diastole (using M-mode), left atrium and aortic root dimensions (using 2D), and maximum aortic and pulmonary flow velocities (using pulsed-wave spectral Doppler). ECG measurements were similar to those reported for other pinniped species, but there was considerable variation in the MEAs of Steller sea lions and northern fur seals. Echocardiographic measurements were similar to those reported for southern sea lions (Otaria flavenscens), including five out of eight Steller sea lions having a left atrial to aortic root ratio <1, which may indicate that they have an enlarged aortic root compared to awake terrestrial mammals. Isoflurane anesthesia likely affected some of the measurements as evidenced by the reduced fractional shortening found in Steller sea lions compared to awake terrestrial mammals. The values reported are useful reference points for assessing cardiac health in pinnipeds under human care.

Transient deep and giant negative T waves in dogs with myocardial injury

IntroductionAlthough transient deep and giant negative T waves (NTWs) may develop during myocardial injury (MI) in humans, no data exist on this repolarization abnormality in canine MI. Therefore, this study aimed to describe the occurrence of transient deep/giant NTWs in dogs with MI. Animals, Materials and MethodsMedical records were retrospectively searched to identify dogs with MI and transient deep/giant NTWs. Signalment, history, and selected diagnostic test results were reviewed. Data analysis was descriptive. ResultsSix cases were diagnosed with MI associated with deep (n = 1) and giant (n = 5) transient NTWs. Myocardial injury was classified as acute in all cases and was due to snake envenomation (n = 3), sepsis (n = 2), and systemic inflammatory response syndrome (n = 1). At the time of deep/giant NTWs identification, all dogs had elevated cardiac troponin I and ≥1 echocardiographic abnormality of the left ventricular structure and/or function. Moreover, all dogs with giant NTWs had prolonged QT intervals. After the MI resolution, T-wave polarity and QT-interval duration became normalized in all dogs. Moreover, left ventricular morphological and functional parameters were completely normalized in four dogs. In contrast, ventricular echogenicity remained heterogeneous in two dogs, despite otherwise normalized ventricular parameters. Five dogs were still alive at the conclusion of the study. ConclusionsTransient deep/giant NTWs may develop in dogs with acute MI and T-wave polarity changes seem to occur synchronously with the evolution of myocardial damage. Moreover, transient deep/giant NTWs seem associated with a favorable prognosis in canine MI.

Noninvasive unipolar electrogram T-wave upslope is an accurate marker of local refractoriness in explanted hearts with drug-induced repolarization dispersion

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): French National Research Agency Matthijs Cluitmans is supported by a Veni grant from the Netherlands Organization for Scientific Research Background The relationship between T-wave morphology in local unipolar electrograms (UEGs) as mapped with noninvasive electrocardiographic imaging (ECGI) and local repolarization time (RT) has not been validated in pronounced RT dispersion. Purpose To study the time of upslope of the T-wave (Tup) in epicardial UEGs mapped with ECGI as a marker of time of local refractoriness (trefr, a surrogate for RT) in intact hearts with RT dispersion. Methods Six pig hearts were Langendorff-perfused with selective perfusion of the LAD artery and submersed in a torso-shaped tank containing 256 electrodes on the torso surface (panel A). RT was prolonged in the non-LAD regions by infusing dofetilide (‘Dof’) and shortened in the LAD region using pinacidil (‘Pin’). Tup was determined in both invasive UEGs (recorded with epicardial electrodes) and in noninvasive UEGs (reconstructed with ECGI). Programmed stimulation was used to determine trefr, defined as the shortest coupling interval with capture. Both metrics were determined relative to the common pacing spike. Results In all six hearts, selective dofetilide and pinacidil infusion resulted in delayed trefr and Tup in the non-LAD region, and shortened invasive trefr and noninvasive Tup in the LAD region, respectively (panel B and C). Over all 59 observations, Tup showed high agreement with trefr (values close to line of identity, panel D) with strong correlation (r = 0.91). This finding was independent of T-wave polarity (positive, negative or biphasic). Conclusion The moment of steepest upslope of the T-wave in a noninvasively reconstructed UEG accurately reflects end of local refractoriness in intact hearts, in case of pronounced RT dispersion. Under these circumstances, when local RT is defined by moment of re-excitability (allowing to link it to conduction block and re-entry), ECGI T-wave upslope can be taken as a truthful marker for local RT. Abstract Figure. Results

Diagnostic performance of 18-leads electrocardiography to distinguish takotsubo syndrome and acute anterior myocardial infarction

Abstract Background Electrocardiographic (ECG) features on acute phase of Takotsubo syndrome (TTS) is recognized to mimic that of acute anterior myocardial infarction (ant AMI). However, the difference of synthesized 18-leads ECG of both diseases was not elucidated. Purpose To elucidate diagnostic performance of 18-leads ECG to distinguish TTS and acute anterior AMI. Methods We firstly enrolled consecutive 40 patients of TTS, and among 500 ant AMI patients, one to two matching was done by their age and gender. Finally, 40+80 patients (74.5±11.2 years, 87 females) were enrolled, and ECG at onset of both group was estimated. Because of multicollinearity, all significant differences were compared by machine learning (Random Forest method). Results Prevalence of Q wave had no difference. Conversely, ST depression in TTS and ST elevation in ant AMI were significant differences in V7–9 leads. T-wave polarity of V3R-V9 leads were significantly different (flat T-wave in TTS and positive in ant AMI). Machine learning revealed T wave polarity in V7 lead had the highest feature importance. Conclusion 18-leads ECG at onset had powerful diagnostic performance to distinguish the two diseases. Funding Acknowledgement Type of funding source: None

The repolarization pattern of ARVC patients, healthy gene carriers and controls as analyzed with a 252-leads Body Surface Mapping Vest

Abstract Background Repolarization abnormalities have a central role on the diagnosis of ARVC according to recent HRS consensus document from 2019 stating that T wave inversion in the right precordial leads is a major criteria if it appears in V1-V3 or a minor criteria if it appears in only V1-V2. Purpose The aim of our study was to investigate whether repolarization patterns as recorded by a Body Surface Mapping (BSM) system consisting of a vest with 252 ECG leads, could differentiate ARVC patients and even gene carriers from normal individuals. Our hypothesis is that the method can potentially identify repolarization disturbances earlier or better than conventional 12-lead ECG. Method 12 definite ARVC patients, 20 healthy gene carriers and 8 family members who tested negative for the family mutation (controls) were included. All patients underwent 12-lead ECG, including right precordial leads (V4R) and BSM recordings. Repolarization (T-wave polarity and concordance with QRS complex vector) was analyzed qualitatively in all BSM recordings, the results of which were displayed on a color code map (fig.1). Results The mean age was 49.6, 43.6 and 38.8 years in ARVC patients, healthy gene carriers and controls, respectively. The number of males in the three groups were 8/12, 8/20 and 5/8, respectively. All 8 controls had similar repolarization patterns with negative and concordant T waves on the right back panel, and T waves that successively changed from negative concordant (green) to positive disconcordant (red) and finally positive concordant (blue) on the left front panel (pattern 1). All 12 ARVC patients had different repolarization patterns as compared to the controls. Two of these patients had no apparent repolarization changes on conventional 12 lead ECG. The pattern type 2 repolarization, as defined by same pattern as the controls at the right back panel but different pattern at the front left panel was seen in 3/12 ARVC patients. The remaining 9 ARVC patients had different repolarization patterns both on the front and on the back panel (pattern 3). Among gene carriers, 15 had a normal repolarization pattern (pattern 1) and 5 demonstrated an abnormal repolarization pattern (4 had pattern type 2 and one pattern 3) despite normal surface ECG. Conclusions Using BSM recordings, abnormal repolarization patterns can be detected in all ARVC patients, even in those without repolarization changes on conventional surface ECG. The observation that 25% of gene carriers had divergent repolarization patterns, may indicate an early stage of the disease, and be used as an early diagnostic marker of the disease. Further and larger studies are warranted to confirm these observations. Repolarisation patterns recorded by BSM Funding Acknowledgement Type of funding source: Foundation. Main funding source(s): Selanders Stiftelse

Right-to-left T-wave discordance in acute myocardial infarction: A new electrocardiographic sign of apical and left lateral infarction

IntroductionA new ECG method producing Precordial Bipolar Leads (PBL) enables a computerized subtraction of the electrical activity detected by the precordial V1 lead from that of the V6 electrode (V6-V1 PBL). This calculation can also be performed manually using measurements from standard simultaneous 12 lead ECG (SS12LECG) tracings. We compared the magnitude of T-waves generated by PBL V6-V1 (measured by computer) to the SS12LECG V6-V1 T-waves (measured on the tracing) to determine whether these measurements are equivalent. Although Lead I and Lead V6-V1 PBL examine almost the same right-to-left axis, we noted that Lead I and Lead V6-V1 PBL sometimes have opposite T-wave polarities. We investigated this observation further using a database containing control and patient data. Material and methodsRecords of 79 patients and 52 controls from the Physionet database were used to generate the V6-V1 PBL for comparison to manual calculations from the V1 and V6 unipolar T-wave measurements on the tracings. The accuracy of these measurements was validated against the computer measurements by correlation and paired t-tests. ResultsThe T-wave automated and manual measurements in patients were strongly correlated (0.9895), consistent with the premise that measurements from tracings are accurate. The V6-V1 T-wave calculation was positive in 48 of the 52 control subjects. Nearly half of the acute myocardial infarction (AMI) patients had discordant T-wave polarity between Lead I and V6-V1 PBL; ventriculography results on 24 of these patients identified 13 patients with apical and 11 with lateral wall motion abnormalities. ConclusionA discordant T-wave in Lead I and in the V6-V1 PBL is a potential diagnostic criterion for apical or left-lateral infarction.

Lead aVR is a predictor for mortality in heart failure with preserved ejection fraction

BackgroundNormally, lead augmented vector right (aVR) has a negative T wave polarity (TaVR) in the electrocardiography (ECG). Positive TaVR and ST segment deviation in lead aVR (STaVR) have negative effects on mortality in heart failure with reduced ejection fraction patients. AimOur aim was to investigate the relationship between lead aVR changes and mortality in heart failure with preserved ejection fraction (HFpEF) patients. MethodsWe retrospectively examined 249 patients in 2011–2015 years (mean age 70.8±11.9 years and follow-up period 38.3±9.6 months). ECG, echocardiographic, and laboratory findings were recorded and compared in the study. Existence of positive TaVR, STaVR, and quantitative TaVR values were recorded and the absolute numerical values of TaVR and STaVR were recorded from the 12-lead surface ECG (T/STaVR ratio or vice versa). ResultsThe patients were divided into two groups: living (171) and deceased (78). Age, systolic blood pressure, left atrial diameter, QRS duration, positive TaVR frequency, STaVR, absolute value of TaVR, and ratio were significantly higher in the deceased group. Age (OR: 1.106), STaVR (OR: 2.349), TaVR (OR: 1.612), and T/STaVR ratio (OR: 5.156) were determined as independent predictors for mortality. ConclusionsST segment and T wave polarity changes in lead aVR closely associated with mortality in patients with HFpEF.

Correlation between Ventricular Repolarisation Patterns and T-Wave Generation in Isolated Rabbit Hearts using Panoramic Imaging

It is generally accepted that the normal T-wave is the manifestation of repolarisation gradients in the ventricles of the heart in an endocardial- epicardial direction. However, several studies contradict these findings, attributing T-wave polarity to apico-basal and/or interventricular repolarisation gradients. Consequently, the mechanisms responsible for the T-wave under both normal and pathological conditions remain unclear. In this study, isolated Langendorff-perfused rabbit hearts (37oC) were suspended in a customized chamber containing a frame that allowed the heart to be rotated to ±120° from a central position. Epicardial voltage was monitored by staining the heart with voltage sensitive dye (di-4-ANEPPS). Illumination at 480nm was provided by an array of LEDs (OptoLED, Cairn Research Ltd.). Emitted fluorescence was collected, filtered with 590nm long-pass filter and focused on a CCD chip (Redshirt Imaging, Decatur, GA) which acquired images (80x80 pixels) every 1ms. Recordings were made from 3 sides to obtain a panoramic map of cardiac electrical activity. Simultaneously, pseudo-ECG recordings (equivalent to Lead I) were recorded while pacing via electrodes placed on the right atrium. Epicardial ventricular repolarisation patterns were correlated to corresponding ECG recordings. In contrast to some previous studies, less than 5% of the epicardium (right and left ventricles) was repolarised by the peak of the T-wave. In addition, the presence of an apico-basal repolarisation gradient on the left ventricle (LV) developed in the latter half of the T-wave. An inverse relationship between APD and activation time was observed across the LV suggesting that activation pattern is a determinant of epicardial APD. In conclusion, the lack of a prominent epicardial repolarisation gradient during the first half of the T-wave suggests that regions other than the epicardial surface are responsible for the initial deflection.

Dynamic QT/RR relationship in post-myocardial infarction patients with and without cardiac arrest

Objectives. Changes in QT interval dynamicity may be associated with susceptibility to ventricular fibrillation (VF) after myocardial infarction (MI). We tested the hypothesis that dynamic QT/RR relationship might differ between post-MI patients with and without a history of VF. We also evaluated the influence of negative T-waves on the assessment of QT/RR relationship. Design. We reviewed Holter recordings from 37 post-MI patients resuscitated from VF not associated with new MI (VF group) and 30 patients after MI without known sustained ventricular arrhythmias (control group). With an automated computerized program, we measured QT interval dynamicity as the mean QT/RR slope and as the maximal QT/RR slope determined at stable heart rates. Results. The mean QT/RR slope was 0.20 ± 0.08 in control group and 0.15 ± 0.09 in VF group (p=0.01) whereas corresponding maximal QT/RR slope values were 0.42 ± 0.20 and 0.33 ± 0.18 (p=0.01), respectively. Thirteen control patients (43%) and 22 VF patients (59%) showed only negative or both positive and negative T-waves (p=0.45). Mean QT/RR slope values were similar irrespective of T-wave polarity whereas maximal QT/RR slopes were steeper in cases with both positive and negative T-waves. Cases showing T-waves of both positive and negative polarity exhibited greatest intersubject variability of both QT/RR slope values. Conclusions. Lower mean QT/RR slope may be associated with a risk of VF after MI. A detailed assessment and definition of differing T-wave polarities is essential in evaluating the QT/RR relation in post-MI patients.

Type 1 electrocardiographic burden is increased in symptomatic patients with Brugada syndrome

BackgroundSpontaneous type 1 electrocardiographic (ECG) is a risk factor for arrhythmic events in Brugada patients but the importance of the proportion of time with a type 1 ECG is unknown. Patients and MethodsThirty-four Brugada patients (15 symptomatic) underwent a 24-hour 12-lead ECG recording. One-minute averaged waveforms displaying ST-segment elevation above 200 μV, with descending ST-segment and negative T-wave polarity on leads V1-V3 were considered as type 1 Brugada ECG. The burden was defined as the percentage of type 1 Brugada waveforms. ResultsType 1 ECG on lead V2 was more frequent in symptomatic patients (median 80.6% [15.7–96.7] vs 12.4% [0.0–69.7], P = .05). Patients with a permanent type 1 pattern on lead V2 were more likely to be symptomatic (5/6) than patients without type 1 ECG during a 24-hour period (2/9) (P < .05). ConclusionType 1 pattern is more prevalent across a 24-hour period in symptomatic Brugada patients.

Pathophysiology and Clinical Implications of Cardiac Memory

Altering the pattern of activation of the ventricle causes remodeling of the mechanical and electrical properties of the myocardium. The electrical remodeling is evident on the surface electrocardiogram as significant change in T-wave polarity following altered activation; this phenomenon is ascribed to as "T-wave memory" or "cardiac memory." The electrophysiological remodeling following altered activation is characterized by distinct changes in regions proximal (early-activated) versus distal (late-activated) to the site of altered activation. The early-activated region exhibits marked attenuation of epicardial phase 1 notch due to reduced expression of the transient outward potassium current (I(to)). This is attributed to electrotonic changes during altered activation, and angiotensin-mediated regulation of Kv4.3 (the pore-forming alpha subunit responsible for I(to)). The late-activated region exhibits the most significant action potential prolongation due to markedly increased mechanical strain through a mechano-electrical feedback mechanism. Consequently, regionally heterogeneous action potential remodeling occurs following altered activation. This enhances regional repolarization gradients that underlie the electrophysiological basis for T-wave memory. Further, recent clinical studies highlight detrimental consequences of altered activation including worsening mechanical function and increased susceptibility to arrhythmias. Future studies to identify molecular mechanisms that link electrotonic and mechanical strain-induced changes to cellular electrophysiology will provide important insights into the role of altered activation in regulating cardiac repolarization and arrhythmogenesis.

AS-58: The Relationship between T-Wave Polarity and Clinical and Angiographic Findings in Early-Stage Myocardial Infarction

AS-58: The Relationship between T-Wave Polarity and Clinical and Angiographic Findings in Early-Stage Myocardial Infarction

Prolongation of the QTc Interval Is Seen Uniformly During Early Transmural Ischemia

In order to more clearly understand the electrocardiographic manifestations of early transmural ischemia, we studied electrocardiograms (ECGs) in patients undergoing balloon angioplasty. Decisions regarding reperfusion strategies in patients with acute myocardial infarction rely largely on the presence of ST-segment elevation (STE) in the ECG, consequently with significant limitations. Studies of the "ischemic cascade" show that ST-segment changes occur well after the onset of wall motion abnormalities. We prospectively analyzed ECGs obtained at 20-s intervals in 74 patients undergoing elective balloon angioplasty. The ECGs were analyzed using 3 methodologies. In 74 patients, the ST-segment, the T-wave, and the QT-interval were analyzed using the MUSE (General Electric HC, Menomonee Falls, Wisconsin) automated system (MUSE). Fifty patients were also analyzed using the Interval Editor automated system (IE; General Electric HC). In 20 patients, measurements were made manually. Transmural ischemia prolonged the QTc interval (using the Bazett's formula) in 100% of patients. In all 74 patients analyzed with MUSE, QTc interval prolonged from 423 +/- 25 ms to 455 +/- 34 ms (p < 0.001). In the 50 patients analyzed with IE, QTc interval prolonged in 50 of 50 (100%) patients (from 424 +/- 27 ms to 458 +/- 33 ms [p < 0.001]). Mean time to maximal QTc interval prolongation, changes in T-wave polarity, > or =1 mm STE, and ST-segment depression (STD) were 22, 24, 29, and 35 s, respectively. Although QTc interval prolonged in 100% of patients, T-wave changes, STE, and STD (> or =1 mm) occurred in 7%, 15%, and 7%, respectively. The QTc interval prolongs in 100% of patients with early transmural ischemia. When compared with clinically accepted indexes of transmural ischemia (i.e., STD and STE [> or =1 mm]) it is the earliest ECG abnormality.

Usefulness of ST Depression With T-Wave Inversion in Leads V 4 to V 6 for Predicting One-Year Mortality in Non–ST-Elevation Acute Coronary Syndrome (from the Electrocardiographic Analysis of the Global Use of Strategies to Open Occluded Coronary Arteries IIB Trial)

ST-segment depression (ST-D) on the admission electrocardiogram of patients with non-ST-elevation acute coronary syndromes (NSTEACSs) is associated with higher mortality. However, few studies have evaluated the effect of location of ST-D and T-wave polarity on long-term prognosis of patients with NSTEACS. Electrocardiographic (ECG) and clinical data from 6,770 patients with NSTEACS randomly assigned in the Global Use of Strategies to Open Occluded Coronary Arteries (GUSTO) IIB trial were analyzed retrospectively. One-year mortality was correlated with location of ST-D (leads I and aVL; II, III, and aVF; V1 to V3; or V4 to V6) and T-wave polarity. ST-D in any of the ECG locations was associated with higher mortality compared with patients without ST-D. Patients with ST-D and T-wave inversion in leads V4 to V6 had the highest 1-year mortality rate of all groups (16.2%), significantly higher compared with patients with ST-D without T-wave inversion in those leads (9.0%, p=0.001). Logistic regression analysis showed that age, hyperlipidemia, Killip class>I, history of myocardial infarction, history of heart failure, history of angina pectoris, systolic blood pressure, heart rate, sum of ST-D (odds ratio 1.061, 95% confidence interval 1.035 to 1.087, p<0.001), and ST-D with T-wave inversion in leads V4 to V6 (odds ratio 1.374, 95% CI 1.023 to 1.844, p=0.035) were independent predictors of 1-year mortality. Conversely, ST-D without T-wave inversion in leads V4 to V6 or other ECG presentations were not independent predictors of high 1-year mortality. In conclusion, ST-D with T-wave inversion in leads V4 to V6 on the admission electrocardiogram in patients with NSTEACS identifies those with higher 1-year mortality than for patients with any other ECG presentation.

New electrocardiographic criteria for identifying the culprit artery in inferior wall acute myocardial infarction—usefulness of T-wave amplitude ratio in leads II/III and T-wave polarity in the right V 5 lead

ST-segment elevations in the right ventricular lead and those greater in lead III than in lead II strongly suggest that right, rather than left circumflex, coronary arterial occlusion occurs in acute myocardial infarction in the inferior wall. Our study demonstrated that, in the very early stages of infarction, a T-wave amplitude that is greater in lead III than in lead II and an upright or positive biphasic T wave in lead V(5)R are just as predictive as ST-segment changes and are often easier to measure.

QT interval measurement in the dog: Chest leads versus limb leads

Introduction: An accurate measurement of the QT interval is dependent on the accurate identification of the end of the T wave. Although chest leads have been recommended in dog toxicology studies, their use has not been widely put into practice, as shown by a recent survey on methodology for ECG collection in the pharmaceutical industry. Therefore, there is little published data on dog QT measurement from chest leads. Methods: Electrocardiograms (ECGs) were taken from 100 beagle dogs (50 males, 50 females), with the dogs restrained in a sling. On the day of recording, measurements were performed at time zero and 1 h later. Recordings were repeated 7 to 10 days later. QT interval measurements were taken simultaneously from Lead II and the chest Lead CV5RL. Heart rate was taken from Lead II. Statistical analyses included the calculation of a QT correction formula, comparison of the mean values and variability of QT and QTc measurements from Leads II and CV5RL, the comparison of T-wave polarity from both leads, and a power analysis for QT and QTc. Results: The T wave was positive in almost all dogs (99/100) in the Lead CV5RL at all measurement periods, while it was either positive or negative in Lead II (64–75/100), and the incidence of positive T wave varied between measurement periods. The QT interval was significantly shorter (194±11 to 197±12 vs. 197±13 to 200±12 ms) when measured from the CV5RL lead at all recording periods and in both sexes. In addition, the standard deviation for QT measurement within each individual ECG record demonstrates less intra-animal variation when QT is measured from Lead CV5RL compared with Lead II (3.8 vs. 13.2 ms). The linear regression between QT and heart rate was improved when QT measurements were taken from CV5RL, as shown by the percentage of variability R 2. Discussion: Estimates of the sample sizes showed that fewer animals would be required to detect a change at both the high and the mid-doses when using the chest Lead CV5RL. Using Lead II, we are able to detect within-animal changes of 10% in either QT or QTc; with Lead CV5RL, we are able to detect 10% change in QT and 5% change in QTc.