First-degree Atrioventricular Research Articles

AV-optimized conduction system pacing for treatment of AV dromotropathy: A randomized, cross-over study.

Severe first-degree atrioventricular (AV) block may produce symptoms similar to heart failure due to AV dyssynchrony, a syndrome termed AV dromotropathy. According to guidelines, it should be considered for permanent pacemaker implantation, yet evidence supporting this treatment is scarce. This study aimed to determine the impact of AV-optimized conduction system pacing (CSP) in patients with symptomatic severe first-degree AV block and echocardiographic signs of AV dyssynchrony. Patients with symptomatic first-degree AV block (PR > 250 ms), preserved left ventricular ejection fraction, narrow QRS, and AV dyssynchrony were included in the study. In a single-blind cross-over design, patients were randomized to AV sequential CSP or backup VVI pacing with a base rate of 40 bpm. We compared exercise capacity, echocardiographic parameters, and symptom occurrence at the end of 3 months of each period. Fourteen patients completed the study. During the AV-optimized CSP compared to the backup pacing period, patients achieved a higher workload on exercise test (147.2 ± 50.9 vs. 140.7 ± 55.8 W; p = .032), with a trend towards higher peak VO2 (23.3 ± 7.1 vs. 22.8 ± 7.1 mL/min/kg; p = .224), and higher left ventricular stroke volume (LVSV 74.5 ± 13.8 vs. 66.4 ± 12.5 mL; p < .001). Symptomatic improvement was recorded, with fewer patients reporting general tiredness and 71% of patients preferring the AV-optimized CSP (p = .008). AV-optimized CSP could improve symptoms, exercise capacity and LVSV in patients with severe first-degree AV block.

Left ventricular mechanical dispersion as a predictor of the need for pacemaker implantation after transcatheter aortic valve implantation: MeDiPace TAVI study.

Permanent pacemaker (PM) implantation is common after transcatheter aortic valve implantation (TAVI). Left ventricular mechanical dispersion (MeDi) by speckle tracking echocardiography is a marker of fibrosis that causes alterations in the conduction system. We hypothesized that MeDi can be a predictor of the need for PM implantation after TAVI. Consecutively, 200 TAVI patients were enrolled. Transthoracic echocardiography and electrocardiography examinations were recorded before TAVI to evaluate global longitudinal strain (GLS), MeDi, and conduction disturbances. PM implantation information was obtained 3 months after TAVI. Patients were stratified into PM or no PM group. Mean age was 80 + 7 years (44% women). Twenty-nine patients (16%) received PM. MeDi, QRS duration, existence of right bundle branch abnormality (RBBB), and first-degree atrioventricular (AV) block were significantly different between groups. MeDi was 57 ± 15 ms and 48 ± 12 ms in PM and no PM groups, respectively (P < 0.001). In multivariate analysis, MeDi predicted the need for PM after TAVI independently of GLS, QRS duration, RBBB, and first-degree AV block [odds ratio (OR): 1.73, 95% confidence interval (CI): 1.22-2.45] with an area under the curve (AUC) of 0.68 in receiver operating characteristic (ROC) curves. Moreover, RBBB was an independent predictor of PM need after TAVI (OR: 8.98, 95% CI: 1.78-45.03). When added to RBBB, MeDi had an incremental predictive value with an AUC of 0.73 in ROC curves (P = 0.01). MeDi may be used as an echocardiographic functional predictor of the need for PM after TAVI.

Profound First-Degree Atrioventricular Block in a High-Level Basketball Athlete

First-degree atrioventricular (AV) block (PR interval &gt;200 ms) is commonly observed among screening electrocardiogram (ECG) in athletes. Profound first-degree AV block (PR interval &gt;400 ms) and Mobitz type I (Wenckebach) second-degree AV block are generally uncommon and often require further workup on a case-by-case basis, particularly when there is concern for a structural cardiac abnormality. In this case, we present an example of an asymptomatic profound first-degree AV block with Mobitz type I (Wenckebach) second-degree AV block. Transthoracic echocardiogram and stress echocardiogram were unremarkable and the patient was cleared to participate in sports without any restriction. Physicians managing athletes should be aware of ECG features that require additional evaluation and cardiology consultation.

Pseudo-pacemaker syndrome with prolonged PR interval: A narrative review.

Pseudo-pacemaker syndrome (PPMS) is a rare complication of first-degree atrio-ventricular (AV) block in which a very prolonged PR interval causes AV dyssynchrony and subsequent symptoms of hemodynamic instability in the absence of an implanted pacemaker. The aim of this manuscript was to describe a unique case of PPMS and to provide a comprehensive review of the topic to help clinicians in the diagnosis and management of this condition. Through systematic research on PubMed, Google Scholar, EBSCO, and Ovid MEDLINE and using the search strings "pseudo-pacemaker syndrome" and "symptomatic first-degree AV block," we identified 14 articles accounting for 17 cases of PPMS, including our case report. The most common age group for PPMS was middle-aged and young adults, with an average age of 47 years. Palpitations were the most common presenting symptom and four main etiologies of PPMS were identified, as follows: (1) Idiopathic PPMS with evidence of impaired conduction over the AV node (20% of cases), (2) PPMS associated with reversable inflammatory causes (13%) or (3) associated with iatrogenic surgical or interventional procedures leading to the permanent damage of the normal AV conduction system (20%), and, finally, (4) PPM related to dual AV nodal physiology (DAVNP) as a primary finding (27%) or occurring after fast or slow pathway ablation for treatment of AV nodal re-entrant tachycardia (AVNRT) (20%). Treatment should be patient-tailored and based on the specific etiology once identified. However, the treatment of PPMS due to DAVNP without AVNRT presentation is yet to be clarified.

Recognizing Patterns on a Resting 12-Lead Electrocardiogram

Scenario: During an annual physical examination, a healthy 55-year-old man who works as a long-haul truck driver had a routine 12-lead electrocardiogram (ECG) recorded. Overall, he had no complaints and was asymptomatic. His body mass index was within normal limits, and he was taking simvastatin for high cholesterol and lisinopril for high blood pressure (current blood pressure, 128/78 mm Hg).Sinus rhythm at 85 beats per minute with first-degree atrioventricular (AV) block and premature ventricular contractions (PVCs) in a trigeminy pattern.Trigeminy is a pattern of PVCs occurring in a series of 3 heart beats, either 2 normal sinus beats followed by a PVC (as in this example) or 1 normal sinus beat followed by 2 PVCs. Trigeminy is not common, is often transient, and can disturb the normal contraction and cardiac output of the heart because a premature impulse interrupts sinus rhythm. In this case, there are more sinus beats than PVCs, most likely supporting normal cardiac output. The PVCs are similar in morphology, or unifocal, suggesting the origin (focus) is at 1 ventricular site. The etiology of trigeminy is not definitive, but some causes include caffeine, medications (eg, antihistamines), alcohol, anxiety, and heart disease. Of note, the PR interval is slightly prolonged (210 milliseconds), meeting criteria for a first-degree AV block. This occurs when electrical conduction through the AV node is slowed but atrial to ventricular conduction is not interrupted. In this case, the continuous rhythm strip at the bottom of the 12-lead ECG is very helpful in capturing the onset and offset of the PVCs. Also, the low R-wave amplitude may be a sign for hypertensive patients requiring further workup with echocardiography.Although this patient is asymptomatic, options to monitor the patient for a long, continuous period include portable monitors like a Holter or event recorder to improve assessment of the prevalence of the PVCs and other dysrhythmias. Potential modifications that should be recommended to this patient to avoid possible triggers include reducing caffeine intake, managing anxiety, monitoring his blood pressure, and exercising (given the sedentary nature of his profession). In general, first-degree AV block is considered benign, is not traditionally treated, and in this case was not new. However, recent epidemiological research from the Framingham study indicates a relationship between first-degree AV block and a higher risk of hospitalization for heart failure, cardiovascular mortality, and all-cause mortality. Although currently asymptomatic, the patient should monitor for potential symptoms of worsening of cardiovascular health, for example, new-onset palpitations. If symptoms develop and evidence suggests more sustained arrhythmia, an echocardiogram may be warranted.

AV timing in pacemaker patients with first-degree AV block: which is preferable, intrinsic AV conduction or pacing?

Some patients with pacemakers present with first-degree atrioventricular (AV) block. To avoid right ventricular (RV) pacing, preserving intrinsic AV conduction as much as possible is recommended. However, there is no clear cutoff AV interval to determine whether intrinsic AV conduction should be preserved or RV pacing should be delivered. This study aimed to compare a pacing mode-preserving, intrinsic AV conduction with the DDD mode delivering RV pacing in terms of echocardiographic parameters in patients with first-degree AV block and to investigate whether RV pacing induces heart failure (HF). Stroke volume (SV) was measured to determine the optimal AV delay with the intrinsic AV conduction rhythm and the DDD pacing delivering RV pacing. Echocardiographic evaluation was performed for 6-month follow-up period. Seventeen patients were studied. At baseline, mean intrinsic PQ interval was 250 ± 40 ms. SV was greater with RV pacing with optimal AV delay of 160 ms than with intrinsic AV conduction rhythm in all patients. Therefore, pacemakers were set to the DDD to deliver RV pacing. During follow-up, seven patients developed HF. Mean baseline E/E′ ratio in patients who developed HF (HF group) during RV pacing was higher than in patients without HF (non = HF group; 17.9 ± 8 versus 11.5 ± 2, P = 0.018) Even within HF group patients without a high baseline E/E′ ratio, it increased with RV pacing (22.2 ± 6 versus 11.6 ± 2; P < 0.001). In patients with pacemaker and first-degree AV block, RV pacing with the optimal AV delay of 160 ms increased SV. However, the risk of HF may be increased with RV pacing if the E/Eʹ ratio is > 15 during intrinsic AV conduction or RV pacing. RV pacing should be avoided in patients with high E/Eʹ ratio under intrinsic AV conduction or RV pacing.

Epicardial fat volume is associated with preexisting atrioventricular conduction abnormalities and increased pacemaker implantation rate in patients undergoing transcatheter aortic valve implantation

Epicardial fat tissue (EFT) is a highly metabolically active fat depot surrounding the heart and coronary arteries that is related to early atherosclerosis and adverse cardiac events. We aimed to investigate the relationship between the amount of EFT and preexisting cardiac conduction abnormalities (CCAs) and the need for new postinterventional pacemaker in patients with severe aortic stenosis planned for transcatheter aortic valve implantation (TAVI). A total of 560 consecutive patients (54% female) scheduled for TAVI were included in this retrospective study. EFT volume was measured via a fully automated artificial intelligence software (QFAT) using computed tomography (CT) performed before TAVI. Baseline CCAs [first-degree atrioventricular (AV) block, right bundle branch block (RBBB), and left bundle branch block (LBBB)] were diagnosed according to 12-lead ECG before TAVI. Aortic valve calcification was determined by the Agatston score assessed in the pre-TAVI CT. The median EFT volume was 129.5 ml [IQR 94–170]. Baseline first-degree AV block was present in 17%, RBBB in 10.4%, and LBBB in 10.2% of the overall cohort. In adjusted logistic regression analysis, higher EFT volume was associated with first-degree AV block (OR 1.006 [95% CI 1.002–1.010]; p = 0.006) and the need for new pacemaker implantation after TAVI (OR 1.005 [95% CI 1.0–1.01]; p = 0.035) but not with the presence of RBBB or LBBB. EFT volume did not correlate with the Agatston score of the aortic valve. Greater EFT volume is associated independently with preexisting first-degree AV block and new pacemaker implantation in patients undergoing TAVI. It may play a causative role in degenerative processes and the susceptibility of the AV conduction system.

First-degree atrioventricular block in children and adolescent athletes

Abstract Introduction Intense regular training produces cardiac adaptations that manifests in various changes in the electrocardiogram (ECG), with sinus bradycardia being the most common finding. In adults the PR interval may be elongated and according to different series it can occur in 10–33% of cases, in the contrary in children and adolescent athletes the prevalence categorized by age has not been studied. Purpose Determine the incidence of first-degree atrioventricular (AV) block in a population of children and adolescent athletes in our environment, categorized by age. Methods We performed a cross-sectional study involving children and adolescent athletes between 5 and 16 years old who received a sport medical examination between August 2018 and May 2019. The ECG were obtained and analyzed following international standards, adequate electrode placement was ensured and was interpreted by cardiologists. The PR interval was obtained, considering prolonged if PR&amp;gt;180 milliseconds (ms) in children under 10 years old, PR&amp;gt;190 ms between 10 and 14 and PR&amp;gt;200 ms in those over 14. We categorized our athletes by age into the following four groups corresponding to approximated quartiles: G1 5–8 years, G2 9–11 years, G3 12–13 years, and G4 14–16 years Results A total of 6401 subjects were included, mean age was 11.2±2.9 years, 93.7% were male, soccer players (97.2%) and Caucasian (99.2%). They trained a mean of 5.4±2.3 hours a week. 11.4% of the patients had mild (50–59 bpm) or moderate (40–49 bpm) bradycardia, but none had severe bradycardia (&amp;lt;40 bpm). Sixty-one patients (0.96%) had 1st degree AV block and 19 (0.30%) had a PR interval at higher limit of normality. When stratified by age groups, the prevalence of 1st degree AV block was higher in the second quartile (Table 1). We did not find cases of Wenckebach or high-grade AV block (Mobitz II or 3rd degree AV block). Conclusions In children and adolescent athletes, the incidence of first-degree AV blockade is low (around 1%) and significantly lower than what is reported in adults. This may be due to a lower vagal tone in this population. If detected it may prompt clinicians to pursue further investigation given the low proportion of 1st degree AV block in children and adolescent athletes. Figure 1. Sixteen year old patient ECG Funding Acknowledgement Type of funding source: None

Recurrent syncope, which patient should we follow more closely

Abstract Introduction The importance of education is well recognized in patients presenting with syncope, in order to reduce the recurrence rate. Purpose To determine a predictive score of recurrent syncopal episodes after the first medical assessment. Methods We conducted a retrospective study enrolling patients followed in our Syncope Consultation from January 2015 to November 2019. Clinical and episodes characteristics, as well as diagnostic studies were analysed. Correlation between variables was performed by the Chi-square and T-Student tests, with a significance level of 95%. Independent predictors of recurrent syncope were identified through a binary logistic regression analysis, considering p=0.05. Then, a discriminatory function was applied using the Wilks lambda test to determine the discriminant score of the analysed groups. SPSS 24.0 was used for statistical analysis. Results A total of 694 patients were included, and 420 (60.5%) had recurrent syncope at the first evaluation. After educational approach, 97 (14%) maintained recurrent episodes. In this subgroup, the mean age was 63.7±22.8 years-old and 88.7% already had previous recurrent syncope (vs 56.1%; p&amp;lt;0.001). The prodrome of malaise was common (40.2% vs 26.8%; p=0.008), but 32% of these patients had syncope without prodromes (vs 21.8%; p=0.032). They also had frequently first-degree atrioventricular (AV) block (22.5% vs 6.8%; p&amp;lt;0.001) and 51.7% had a final diagnosis of reflex syncope. No previous medication with calcium channel blockers (CCB) (p&amp;lt;0.001), malaise (p=0.011), not having Q-waves in the electrocardiogram (p=0.022) and the presence of first-degree AV block (p&amp;lt;0.001) were independent predictors of recurrent syncope. A predictive score of recurrence was determined using the formula: 0.108 − 1.556 x (medication with CCB) + 0.989 x (malaise) − 1.031 x (Q-waves) + 2.406 x (first degree AV block). Variables should be replaced by 1 or 0, depending on whether the condition is present or not. A cut-off of 0.283 was obtained with a specificity of 96.1% and a discriminative power of 81.2%. Conclusion In our patients presenting with syncope, recurrence rate reduced from 60,5% to 14% just with educational measures. To help identify patients who maintain recurrence, we determined a predictive score using clinical data from the first visit, with a good discriminative power and excellent specificity. It could be used to strengthen education, to direct diagnostic studies and to shorten follow-up visits, but it still needs validation to be used in clinical practice. Funding Acknowledgement Type of funding source: None

Inferior ST-Segment Elevation Myocardial Infarction with First-Degree Atrioventricular Block: A Case Report and Literature Review

Background: Atrioventricular (AV) block complicating acute inferior wall ST-elevation myocardial infarction (STEMI) is known to be associated with poor outcomes and increased rate of mortality.&#x0D; Case Report: We present the case of a 69-year old male patient, an active smoker, presented to the emergency department due to syncope 2 hours prior to admission. He reported symptoms while farming with sudden onset of diaphoresis, mild dizziness, and breathlessness followed by loss of consciousness for several minutes. Blood pressure was 79/55 mmHg, respiratory rate was 23, pulse was 46 bpm. Electrocardiogram showed inferior wall STEMI with first-degree AV block. Laboratory data revealed a significantly marked increase of CK-MB 82,5 U/L. STEMI protocol and fibrinolytic therapy has been done. The mechanisms of AV block and its spontaneous resolution in the setting of acute inferior wall STEMI are discussed. Attention is drawn to the patient due to our hospital categorized as an incapable cath lab sub-district hospital.&#x0D; Discussion: Clinical signs and examination suggested that this patient had a first-degree AV block complicating inferior wall STEMI on admission and fulfill the criteria of successful reperfusion 30 minutes following fibrinolytic therapy. Immediately after fibrinolysis, breathlessness was relieved, ST-T segment was reduced, spontaneous resolution of first-degree AV block occurred, and absence of Q-wave formation.&#x0D; Conclusion: Immediate reperfusion therapy is the core management of STEMI patients, including fibrinolytic therapy. Signs of successful therapy could be seen in this case and also relieved of the complication associated with STEMI. We found it as an incidence not much reported and thus reporting the case herewith.

First-degree atrioventricular block on basal electrocardiogram predicts future arrhythmic events in patients with Brugada syndrome: a long-term follow-up study from the Veneto region of Northeastern Italy.

This study was designed to assess the prognostic value of clinical and electrocardiographic parameters in Brugada syndrome (BrS). The study population included 272 consecutive patients (82% males; mean age 43 ± 12 years), with either a spontaneous (n = 137, 50%) or drug-induced (n = 135, 50%) Type 1 Brugada electrocardiogram (ECG) pattern. The study combined endpoint included sudden cardiac death (SCD), cardiac arrest, and appropriate intervention of implantable cardioverter-defibrillator (ICD). A first-degree atrioventricular (AV) block (PR = 219 ± 17 ms) was documented at basal ECG in 45 patients (16.5%); 27 of these underwent an electrophysiological study with recording in 21 (78%) of an HV interval ≥55 ms (mean 61 ± 3 ms). Patients with first-degree AV block had a wider QRS complex (median 110 ms vs. 95 ms; P = 0.04) and more often showed a left anterior hemiblock pattern (n = 13, 29% vs. n = 35, 16%; P = 0.056). During a mean follow-up of 85 ± 55 months, 17 patients (6.3%) experienced ≥1 major arrhythmic events (appropriate ICD intervention, n = 13 and SCD, n = 4). At univariate analysis, the occurrence of major arrhythmic events was significantly associated with a history of syncope or cardiac arrest (P < 0.001), Type 1 ECG pattern (P = 0.04), and first-degree AV block (P < 0.001). Univariate and multivariable predictors of events included a history of syncope or cardiac arrest [hazard ratio (HR) 5.8, 95% confidence interval (95% CI) 2.04-16.5; P < 0.001; and HR 6.68, 95% CI 2.34-19.1; P < 0.001; respectively], a spontaneous Type 1 ECG pattern (HR 1.56, 95% CI 1.03-4.24; P = 0.033; and HR 1.84, 95% CI 1.01-4.29; P = 0.044; respectively) and a first-degree AV block at baseline ECG (HR 3.84, 95% CI 1.47-9.99; P = 0.006; and HR 4.65, 95% CI 2.34-19.1; P = 0.002; respectively). Besides a history of cardiac arrest or syncope, first-degree AV block on basal ECG is an independent predictor of malignant arrhythmic events and a stronger marker of arrhythmic risk than a spontaneous 'coved-type' ECG pattern in patients with BrS.

Abstract 250: Role of First Degree Atrioventricular Block and Long Term Mortality in U.S. Veterans With Atherothrombotic Risk Factors

Background: First-degree atrioventricular (AV) block [PR interval exceeding 200 milliseconds (ms)] on a 12-lead electrocardiogram is a common finding. Previous studies suggested that first-degree AVB has a benign prognosis, but more recent reports suggest that first-degree AVB may be associated with adverse outcomes. We investigated the relationship between PR interval and long term morality in U.S. Veterans with atherothrombotic risk factors. Methods: We retrospectively collected and analyzed data from a Veterans Affairs (VA) medical center for consecutive patients (October 2001 to January 2005) who presented for coronary angiography. Results: Of 1193 charts, 1082 had a PR interval reading recorded (mean = 172.5±30.5 ms; median = 168 ms [range 59-334]). Mean follow-up period was 103±52 months. Mean age was 63.2±10.8 years with 98% male. Mean body mass index was 30.0±5.9. The prevalence of selected comorbidities was: hypertension (88%), hyperlipidemia (79%), obstructive coronary artery disease (73%), diabetes mellitus (45%), smoker (39%), history of peripheral vascular disease (17%), and history of cerebrovascular accident (8%). Mean left ventricular ejection fraction was 47%±13%. Eighty-two percent were on beta-blockers (BB), and 25% were on calcium channel blockers (CCB) while intraventricular conduction delay was seen in 6%. In a comparison of patients with PR interval ≤200 ms (n=936) vs. &gt;200 ms (n=146), long term mortality was higher with PR interval &gt;200 ms (58.2% vs. 44.4%, p=0.002). Mortality rate was also higher with patients on BB or CCB vs. not on either (49.8% vs 39.7%, p=0.024). While PR interval was a significant univariate predictor of mortality, it was not significant when adjusted for the covariates listed above [not including BB and CCB] (odds ratio = 1.08 [95% Cl = 0.70 to 1.66], p = 0.73). Conclusion: In this study of US Veterans with atherothrombotic risk factors, the long term mortality rate was higher with first-degree AV block. PR interval has prognostic value within this specific cohort.

Preexcitation syndrome with myocardial infarction complicated by atrioventricular block in both normal and accessory pathways?

The preexcitation syndrome may either simulate myocardial infarction (MI) or mask it. The rapid anterograde conduction through accessory pathway may obscure atrioventricular (AV) block of the normal AV-nodal tract. To our knowledge, the case of various degree AV-nodal and bypass tract block after MI in a patient with preexcitation syndrome has been infrequently reported. We report a complex case of preexcitation syndrome presenting with first-degree and transient third-degree AV blocks in both normal and accessory pathways after acute MI. Subsequently, we further discuss the diagnosis of MI in preexcitation syndrome and analyze the electrocardiographic character of AV block in preexcitation syndrome.

First‐Degree AV Block—An Entirely Benign Finding or a Potentially Curable Cause of Cardiac Disease?

First-degree atrioventricular (AV) block is a delay within the AV conduction system and is defined as a prolongation of the PR interval beyond the upper limit of what is considered normal (generally 0.20 s). Up until recently, first-degree AV block was considered an entirely benign condition. In fact, some complain that it is a misnomer since there is only delay and no actual block in the AV conduction system (usually within the AV node). However, it has long been acknowledged that extreme forms of first-degree AV block (typically a PR interval exceeding 0.30 s) can cause symptoms due to inadequate timing of atrial and ventricular contractions, similar to the so-called pacemaker syndrome. Consequently, the current guidelines state that permanent pacemaker implantation is reasonable for first-degree AV block with symptoms similar to those of pacemaker syndrome or with hemodynamic compromise, but also stresses that there is little evidence to suggest that pacemakers improve survival in patients with isolated first-degree AV block. Recent reports suggest that it may be time to revisit the impact of first-degree AV block. Also, several findings in post hoc analyses of randomized device trials give important insights in possible treatment options. The present review aims to provide an update on the current knowledge concerning the impact of first-degree AV block and also to address the issue of pacing in patients with this condition.

Atrioventricular conduction and cardiovascular mortality: Assessment of recovery PR interval is superior to pre-exercise measurement

A prolonged electrocardiographic PR interval at rest has been considered a benign phenomenon until recently. We hypothesized that measurement of the PR interval during recovery from physical exertion could improve cardiovascular mortality risk stratification because it would track the dynamic influences of homeostatic mechanisms controlling atrioventricular (AV) conduction. A total of 1,979 consecutive patients (1,244 men and 735 women) with clinically indicated bicycle ergometer tests enrolled in FINCAVAS (the Finnish Cardiovascular Study) were included in the study. The PR interval was measured at 1 min before and at 2 min after exercise. During the mean follow-up period of 47 months (interquartile range: 37 to 59 months), 50 cardiovascular deaths (end point) were registered. The unadjusted hazard ratios (HR) in Cox regression analyses were significant for both continuous PR interval and first-degree atrioventricular (AV) block for pre- and post-exercise phases. After adjustment for standard markers, the PR interval for 20-ms increments (HR: 1.17, P = .117) and first-degree AV block (HR: 1.85, P = .138) during the pre-exercise phase were not prognostic. However, during recovery from exercise, prolonged AV conduction achieved significance both in continuous (HR: 1.29, P = .006) and dichotomized analyses (HR: 2.41, P = .045). The PR interval before exercise is not a robust risk stratifier for cardiovascular death during 4-year follow-up. Post-exercise assessment of AV conduction may offer improved prediction because of functional abnormalities that become manifest only during this physiologic challenge to the heart.

Pseudopacemaker syndrome and marked first-degree atrioventricular block: Case report

Pacemaker syndrome consists of the symptoms and signs present in the single chamber (VVI) pacemaker patient with electrode placed in the right ventricular apex. It is caused by inadequate timing of atrial and ventricular contractions. Pacemaker syndrome without a pacemaker (or pseudopacemaker syndrome) refers to occurrence of symptoms in the presence of marked first-degree atrioventricular (AV) block, when P wave is too close to the preceding QRS complex producing the same haemodynamic disturbance as artificial pacemaker cardiac stimulation with retrograde VA conduction. We present the patient with acute inferior myocardial infarction due to late bare metal stent thrombosis, treated with primary pectutaneous coronary intervention. Hospital course was complicated by complete heart block which was treated with temporary pacing. During the stand-by mode of temporary pacing, sinus rythm with marked first-degree AV block (PQ interval 480 ms) was observed while the patients re-experienced the symptoms that were present prior to pacemaker implantation. Temporary pacing was continued for the next 24 hours when spontaneous shorteninig of PQ interval (250-270 ms) was noticed; since the patient was asymptomatic during the stand-by mode, the pacemaker electrodes were removed and the patient discharged 11 days after admission. Conduction disturbances, such as the varying degrees of AV blocks, are relatively common in acute inferior myocardial infarction. The first degree AV blok is usually asymptomatic and does not require treatment, unless when it is associated with pseudopacemaker syndrome. In that case, temporary pacing provides haemodynamic stability until conduction system recovers.

Diagnostic precision of Doppler flow echocardiography in fetuses at risk for atrioventricular block

To investigate the diagnostic precision of three Doppler methods in their ability to predict postnatal first-degree atrioventricular (AV) block. This was a prospective, observational study carried out from December 1999 to March 2008, including 95 fetuses of anti-SSA/Ro positive mothers undergoing weekly fetal echocardiograms at 18-24 weeks' gestation. Doppler-derived AV time intervals for left ventricular inflow (MV), inflow and outflow (MV-Ao) and superior vena cava a-wave to aortic flow (SVC-Ao) were compared with the PR interval on postnatal electrocardiography. Reference values for MV intervals were established from 102 healthy fetuses, with previously published reference ranges used for the two other methods. Bayesian and receiver-operating characteristics (ROC) curve analyses were performed. The prevalence of first-degree AV block at birth was 13.8%. Using a cut-off at the upper 95% confidence limit, MV-Ao and SVC-Ao time intervals had a sensitivity of 91.7%, and negative predictive value and negative likelihood ratio of 98.4% and 0.10, respectively. The corresponding positive predictive value/positive likelihood ratio for MV-Ao and SVC-Ao were 42.3%/4.5 and 47.8%/5.7, respectively. The areas under the ROC curve (AUC) for MV-Ao and SVC-Ao were 0.87 and 0.89, respectively (both P < 0.001), with generated cut-offs for abnormal AV time intervals at 134-138 and 132-138 ms. MV time intervals using a cut-off at the upper 95% confidence limit had a sensitivity of just 50% and an AUC of 0.74 (P < 0.01). The MV-Ao and SVC-Ao Doppler methods make it possible to identify nearly all fetuses with first-degree AV block at birth and to exclude conduction disturbances in the case of a normal AV time measurement but at the cost of a positive predictive value of 50%.

Second diastolic pulmonary venous flow and isolated late diastolic mitral valve regurgitation in first-degree atrioventricular block

The authors report the case of a 77-year-old male patient with sinus rhythm and a first-degree atrioventricular (AV) block who was referred for echocardiographic follow-up 18 years after aortic valve replacement. Left ventricular systolic function as well as the function of the aortic prosthesis was normal. Systolic mitral regurgitation (MR) was virtually absent, but isolated late diastolic MR was detected by colour Doppler imaging. Coincidental to the occurrence of diastolic MR, a second late diastolic forward flow in the pulmonary veins was observed. Therefore, during the prolonged left atrial relaxation caused by first-degree AV block, the left atrial pressure drops below the pressure in both adjacent chambers in late diastole, resulting in both late diastolic MR and a second diastolic pulmonary venous forward flow.

Electrolyte Imbalances

Scenario: A relatively healthy 82-year-old man presents with complaints of weakness, occasional confusion, and diarrhea. The only medication he reports taking is a “water pill” (spironolactone) for high blood pressure. However, he admits that although instructed to not eat bananas while taking his “water pill,” he has recently returned from a Caribbean cruise where he could not resist eating a banana every day.Interpretation: Normal sinus rhythm (65 beats per minute), first-degree atrioventricular (AV) block, prior anterior wall infarction, and ST-T contours suggesting hyperkalemia.The criteria for first-degree AV block has been met with a lengthened PR interval greater than .20 seconds (atrial depolarization delays are often seen in early phases of hyperkalemia). In addition, prior anterior wall infarction is evident in leads V2 and V3 because there are no R waves. The peaked T waves on this ECG waveform suggest hyperkalemia. Symmetrical peaking of T waves can be mistaken for hyperacute T waves caused by myocardial ischemia; in hyperkalemia, T-wave abnormalities are global rather than regional, as in ischemia. Characteristic ECG changes occur at various levels of hyperkalemia (serum K > 5.5 mEq/L). At serum potassium levels of 6 mEq/L, the ST segments disappear and the T waves become tall and peaked. At levels of 6.5 mEq/L, the P waves begin to flatten out and widen. Sinus arrest may occur when the serum potassium level reaches about 7.5 mEq/L, and cardiac standstill or ventricular fibrillation may occur when serum levels reach 10 to 12 mEq/L. Given that the patient failed to comply with his dietary restriction of no potassium (no bananas), it is prudent to evaluate the patient for hyperkalemia.Initial management is aimed at normalizing the patient’s serum potassium level (3.5–5.5 mEq/L) either pharmacologically or with dialysis. Careful, continuous cardiac monitoring should be maintained to detect dangerous cardiac arrhythmias. After such measures, attention should be focused on removing potassium from the body and managing the condition that led to hyperkalemia. In this case, given the patient’s affinity for bananas, a non–potassium-sparing diuretic may be more appropriate for the management of his hypertension.

Complete heart block: determinants and clinical impact in patients with hypertrophic obstructive cardiomyopathy undergoing nonsurgical septal reduction therapy

ObjectivesThe purpose of this paper is to examine the incidence and determinants of permanent complete heart block (CHB) after nonsurgical septal reduction therapy (NSRT), and to evaluate the clinical impact of permanent pacemaker (PPM) placement. BackgroundNonsurgical septal reduction therapy with ethanol improves the clinical and hemodynamic parameters in patients with symptomatic hypertrophic obstructive cardiomyopathy. Complete heart block is a common complication after NSRT. MethodsThe database of 261 consecutive patients who underwent NSRT at Baylor College of Medicine was reviewed. Clinical variables that were considered as possible determinants for CHB after NSRT were: age, gender, New York Heart Association (NYHA) functional class, left ventricular outflow tract (LVOT) gradient at rest or with provocation, septal thickness, and baseline exercise duration. For electrocardiographic (ECG) variables, the presence of first-degree atrioventricular (AV) block, bifascicular block, left bundle branch block, atrial fibrillation, and left ventricular hypertrophy were analyzed. In addition, the volume of ethanol injected, the method of administration of ethanol (i.e., bolus vs. slow injection [over 30 to 60 s]), number of septal arteries occluded, use of myocardial echocardiography, and infarct size as determined by peak creatine kinase level. ResultsOf 261 consecutive patients, 37 had PPM or automatic implantable cardiac defibrillator placed before NSRT. Of the remaining 224 patients, 31 (14%) developed CHB after the procedure. Multivariate logistic regression analysis showed that female gender (odds ratio [OR] 4.3; p = 0.02), bolus injection of ethanol (OR 51; p = 0.004), injecting more than one septal artery (OR 4.6; p = 0.016), the presence of left bundle branch block (OR 39; p = 0.002), and first-degree AV block (OR 14; p = 0.001) on the baseline ECG are independent predictors of CHB after NSRT. Patients requiring PPM placement had a similar improvement in their NYHA functional class, septal thickness reduction, LVOT gradient reduction, and improvement of exercise capacity when compared with patients who did not require pacing. ConclusionsMultiple demographic, electrocardiographic, and technical factors seem to increase the risk of CHB after NSRT. Patients with CHB after NSRT derive similar clinical and hemodynamic benefit to patients who did not require permanent pacing.