Abstract P556: Temporal and Global Trends of the Incidence of Sudden Cardiac Death in Hypertrophic Cardiomyopathy: A Meta-Analysis

Introduction: Since hypertrophic cardiomyopathy(HCM) initial description, sudden cardiac death (SCD) has been the most feared complication of HCM.

Hypothesis: Temporal, geographical, and age-related trends of SCD rates in HCM have drastically decreased over time.

Methods: Databases were systematically searched to Nov 2021 for studies reporting on SCD event rates in HCM. Patients with SCD equivalents (appropriate ICD shocks and non-fatal SCD) were excluded. Random-e!ects model was utilized to pool study estimates calculating the overall incidence rates(IR) for each time-era, geographical region, and age-group. We analyzed 2 eras (before vs. after 2000, following implementation of ICD in HCM). Following 2000, 5-year intervals were used to reflect the temporal change in SCD.

Results: 98 studies(N=70,510patients and 431,407patient-years) met inclusion criteria. Overall rate of HCM SCD was 0.43%/year (95% CI: 0.37-0.50%; I2=75%; SCD events:1,938; person-years of follow-up: 408,715), with young patients(<18 years) demonstrating a>2-fold-risk for SCD vs. adults(18- 60years) (IR:1.09%; 95% CI: 0.69-1.73% vs. IR: 0.43%; 95% CI: 0.37-0.50%)(P-value for subgroup di!erences:<0.01). Contemporary SCD rates from 2015-present were 0.32%/year; significantly lower compared to 2000 or earlier (IR: 0.32%; 95% CI:0.20-0.52%, vs. IR: 0.73%; 95% CI:0.53-1.02%,respectively). Reported HCM-SCD rates were lowest in North America (IR: 0.28%;95% CI:0.18-0.43%) and highest in Asia(IR: 0.67%; 95% CI:0.54-0.84%).

Conclusions: Contemporary HCM-related SCD are low (0.32%/year) representing a 2-fold decrease compared to prior treatment eras, with young HCM patients at the highest risk. SCD risk stratification maturation and primary prevention ICD application are likely responsible for the notable decline in SCD trends. Moreover, worldwide geographical disparities in SCD was evident, underscoring the need to increase access to SCD prevention for all HCM patients.

Temporal and Global Trends of the Incidence of Sudden Cardiac Death in Hypertrophic Cardiomyopathy

BACKGROUND

Since the initial clinical description of hypertrophic cardiomyopathy (HCM) over 60 years ago, sudden cardiac death (SCD) has been the most visible and feared complication of HCM.

OBJECTIVES

This study sought to characterize the temporal, geographic, and age-related trends of reported SCD rates in adult HCM patients.

METHODS

Electronic databases were systematically searched up to November 2021 for studies reporting on SCD event rates in HCM patients. Patients with SCD equivalents (appropriate implantable cardioverter-defibrillator [ICD] shocks and nonfatal cardiac arrests) were not included. A random-effects model was used to pool study estimates calculating the overall incidence rates (IR) for each time-era, geographic region, and age group. We analyzed 2 periods (before vs after 2000, following clinical implementation of ICD in HCM). Following 2000, 5-year intervals were used to demonstrate the temporal change in SCD rates.

RESULTS

A total of 98 studies (N = 70,510 patients and 431,407 patient-years) met our inclusion criteria. The overall rate of HCM SCD was 0.43%/y (95% CI: 0.37-0.50%/y; I² = 75%; SCD events: 1,938; person-years of follow-up: 408,715), with young patients (<18 years of age) demonstrating a >2-fold-risk for sudden death vs adult patients 18-60 years of age (IR: 1.09%; 95% CI: 0.69%-1.73% vs IR: 0.43%; 95% CI: 0.37%-0.50%) (P value for subgroup differences <0.01). Contemporary SCD rates from 2015 to present were 0.32%/y and significantly lower compared with 2000 or earlier (IR: 0.32%; 95% CI: 0.20%-0.52% vs IR: 0.73%; 95% CI: 0.53%-1.02%, respectively). Reported SCD rates for HCM were lowest in North America (IR: 0.28%; 95% CI: 0.18%-0.43%,) and highest in Asia (IR: 0.67%; 95% CI: 0.54%-0.84%).

CONCLUSIONS

Contemporary HCM-related SCD rates are low (0.32%/y) representing a 2-fold decrease compared with prior treatment eras. Young HCM patients are at the highest risk. The maturation of SCD risk stratification strategies and the application of primary prevention ICD to HCM are likely responsible for the notable decline over time in SCD events. In addition, worldwide geographic disparities in SCD rates were evident, underscoring the need to increase access to SCD prevention treatment for all HCM patients.

Clinical Course and Quality of Life in High-Risk Patients With Hypertrophic Cardiomyopathy and Implantable Cardioverter-Defibrillators

BACKGROUND

High-risk patients with hypertrophic cardiomyopathy (HCM) are identified by contemporary risk stratification and effectively treated with implantable cardioverter-defibrillators (ICDs). However, long-term HCM clinical course after ICD therapy for ventricular tachyarrhythmias is incompletely understood.

METHODS AND RESULTS

Cohort of 486 high-risk HCM patients with ICDs was assembled from 8 international centers. Clinical course and device interventions were addressed, and survey questionnaires assessed patient anxiety level and psychological well-being related to ICD therapy. Of 486 patients, 94 (19%) experienced appropriate ICD interventions terminating ventricular tachycardia/ventricular fibrillation, 3.7% per year for primary prevention, over 6.4±4.7 years. Of 94 patients, 87 were asymptomatic or only mildly symptomatic at the time of appropriate ICD interventions; 74 of these 87 (85%) remained in classes I/II without significant change in clinical status over the subsequent 5.9±4.9 years (up to 22). Among the 94 patients, there was one sudden death (caused by device failure; 1.1%); 3 patients died from other HCM-related processes unrelated to arrhythmic risk (eg, end-stage heart failure). Post-ICD intervention, freedom from HCM mortality was 100%, 97%, and 92% at 1, 5, and 10 years, distinctly lower than in ischemic or nonischemic cardiomyopathy ICD trials. HCM patients with ICD interventions reported heightened anxiety in expectation of future shocks, but with intact general psychological well-being and quality of life.

CONCLUSIONS

In HCM, unlike ischemic heart disease, prevention of sudden death with ICD therapy is unassociated with significant increase in cardiovascular morbidity or mortality, or transformation to heart failure deterioration. ICD therapy does not substantially impair overall psychological and physical well-being.

Electrophysiology testing and the National Cardiovascular Data Registry: stimulating, yet inconclusive

In this issue of PACE, Cheng et al. do an impressive job in evaluating clinical variables associated with electrophysiology studies (EPS) performed within 1 month before implantable cardioverter defibrillator (ICD) placement in 33,786 individuals entered into the National Cardiovascular Data Registry for Implantable Cardioverter Defibrillators (NCDR®-ICD) over a 3-year period. Although of great interest, most of the conclusions are by necessity based on conjecture drawn from observations alone, since the inherent, point-in-time structure of the Registry limits the ability to assess accurate longitudinal clinical correlations and outcomes. The fact is, we really do not know why these patients underwent EPS or how the data from these tests were used. In addition to stimulating speculation on the role of EPS in ICD recipients, the present report should promote caution regarding what conclusions can and should be drawn from the NCDR®-ICD in its present format. As constructed, the Registry provides demographic data and clinical elements up to only a fixed point in time. Hence, the ability to draw conclusions is limited by the abundance of disconnected variables and snapshot quality of data in the NCDR.

Utility and safety of axillo-subclavian venous imaging with carbon dioxide (CO) prior to chronic lead system revisions

BACKGROUND

Prior to attempting placement of one or more electrodes to revise existing rhythm control devices, patency of the central veins should be documented, in view of a high incidence of significant chronic occlusions. Since iodinated contrast venography may be contraindicated in select situations, imaging of the axillo-subclavian venous system with gaseous carbon dioxide (CO(2)) was evaluated prospectively in 23 consecutive individuals who were considered for revision of previously implanted pacemaker or automatic cardioverter defibrillator lead systems.

METHODS

Approximately 20 mL of CO(2) were manually infused via CO(2) primed injection tubing into a vein at or above the level of the antecubital fossa ipsilateral to the side of prior lead placements. Digital subtraction imaging over the axillo-subclavian region, lower neck, and mediastinum was performed. Formal interpretation was obtained from one of three interventional radiologists and at least one electrophysiologist.

RESULTS

Significant venous occlusions were identified in five (22%) patients. Vascular access utilized for the subsequent 18 revisions performed included the imaged patent ipsilateral vein in 14 patients and the contralateral, right-sided subclavian venous system in three patients. One patient required epicardial left ventricular lead placement. There were no complications from venography.

CONCLUSIONS

Axillo-subclavian venography with gaseous CO(2) in patients undergoing pacemaker or implantable cardioverter defibrillator lead revisions is feasible and safe when use of iodinated dye is contraindicated. This technique should be employed in patients with azotemia, dye contrast allergies, or significant inflammation in the vicinity of the intravenous line insertion.

Implantable cardioverter-defibrillators and prevention of sudden cardiac death in hypertrophic cardiomyopathy

CONTEXT

Recently, the implantable cardioverter-defibrillator (ICD) has been promoted for prevention of sudden death in hypertrophic cardiomyopathy (HCM). However, the effectiveness and appropriate selection of patients for this therapy is incompletely resolved.

OBJECTIVE

To study the relationship between clinical risk profile and incidence and efficacy of ICD intervention in HCM.

DESIGN, SETTING, AND PATIENTS

Multicenter registry study of ICDs implanted between 1986 and 2003 in 506 unrelated patients with HCM. Patients were judged to be at high risk for sudden death; had received ICDs; underwent evaluation at 42 referral and nonreferral institutions in the United States, Europe, and Australia; and had a mean follow-up of 3.7 (SD, 2.8) years. Measured risk factors for sudden death included family history of sudden death, massive left ventricular hypertrophy, nonsustained ventricular tachycardia on Holter monitoring, and unexplained prior syncope.

MAIN OUTCOME MEASURE

Appropriate ICD intervention terminating ventricular tachycardia or fibrillation.

RESULTS

The 506 patients were predominately young (mean age, 42 [SD, 17] years) at implantation, and most (439 [87%]) had no or only mildly limiting symptoms. ICD interventions appropriately terminated ventricular tachycardia/fibrillation in 103 patients (20%). Intervention rates were 10.6% per year for secondary prevention after cardiac arrest (5-year cumulative probability, 39% [SD, 5%]), and 3.6% per year for primary prevention (5-year probability, 17% [SD, 2%]). Time to first appropriate discharge was up to 10 years, with a 27% (SD, 7%) probability 5 years or more after implantation. For primary prevention, 18 of the 51 patients with appropriate ICD interventions (35%) had undergone implantation for only a single risk factor; likelihood of appropriate discharge was similar in patients with 1, 2, or 3 or more risk markers (3.83, 2.65, and 4.82 per 100 person-years, respectively; P = .77). The single sudden death due to an arrhythmia (in the absence of advanced heart failure) resulted from ICD malfunction. ICD complications included inappropriate shocks in 136 patients (27%).

CONCLUSIONS

In a high-risk HCM cohort, ICD interventions for life-threatening ventricular tachyarrhythmias were frequent and highly effective in restoring normal rhythm. An important proportion of ICD discharges occurred in primary prevention patients who had undergone implantation for a single risk factor. Therefore, a single marker of high risk for sudden death may be sufficient to justify consideration for prophylactic defibrillator implantation in selected patients with HCM.

Are implantable cardioverter defibrillator shocks a surrogate for sudden cardiac death in patients with nonischemic cardiomyopathy?

BACKGROUND

Ventricular tachyarrhythmias long enough to cause implantable cardioverter defibrillator (ICD) shocks are generally thought to progress to cardiac arrest. In previous ICD trials, shocks have been considered an appropriate surrogate for sudden cardiac death (SCD) because the number of shocks has been thought to be equivalent to the mortality excess in patients without ICDs. The practice of equating ICD shocks with mortality is controversial and has not been validated critically.

METHODS AND RESULTS

The Defibrillators in Non-Ischemic Cardiomyopathy Treatment Evaluation (DEFINITE) trial was a prospective, randomized, multicenter trial of ICD therapy in 458 patients with nonischemic cardiomyopathy. Patients were randomized to receive standard medical therapy (STD) or STD plus an ICD. Shock electrograms were reviewed, and the cause of death was evaluated by a separate blinded events committee. There were 15 SCD or cardiac arrests in the STD group and only 3 in the ICD arm. In contrast, of the 229 patients randomized to an ICD, 33 received 70 appropriate ICD shocks. Patients in the ICD arm were more likely to have an arrhythmic event (ICD shock plus SCD) than patients in the STD arm (hazard ratio 2.12, 95% CI 1.153 to 3.893, P=0.013). The number of arrhythmic events when one includes syncope as a potential arrhythmic event was similar in both groups (hazard ratio 1.20, 95% CI 0.774 to 1.865, P=0.414). Approximately the same number of total events was noted in each arm when we compared syncope plus SCD/cardiac arrest in the STD arm with SCD plus ICD shocks plus syncope in the ICD arm.

CONCLUSIONS

Appropriate ICD shocks occur more frequently than SCD in patients with nonischemic cardiomyopathy. This suggests that episodes of nonsustained ventricular tachycardia frequently terminate spontaneously in such patients.

Roles of hydration, sodium, and chloride in regulation of canine mucociliary transport system

To gain insight into the homeostatic mechanisms regulating airway ion/water fluxes and mucociliary transport, the canine tracheobronchial airway fluid was perturbed by deposition of hypo- and hyperosmotic aerosols for >1 h. Tracheal ciliary beat frequency (CBF) was measured by using heterodyne laser light scattering. Tracheal mucus velocity (TMV) and bronchial mucociliary clearance (BMC) were measured by using radioaerosols and nuclear imaging. Respiratory tract fluid output (RTFO) was collected by using a secretion-collecting endotracheal tube. In six dogs, CBF increased during water deposition in the airways to 180 +/- 30 mg/min and RTFO increased from 2.2 +/- 0.5 to 18.3 +/- 1.6 mg/min, accounting for <10% of the fluid deposition. TMV and BMC were unchanged. CBF, TMV, and BMC were markedly increased by inhalation of aerosolized 3.4 M NaCl. Aerosolized 0.85 M NaCl, in contrast, decreased BMC. In this case, RTFO represented 24% of aerosol deposition. Aerosolized 0.85 M choline chloride and 0.85 M sodium gluconate enhanced BMC and TMV concurrent with a decrease in CBF. RTFO of sodium gluconate studies exceeded 50% of aerosol deposition. Thus the airways appear to have transepithelial compensatory mechanisms that reduce the impact of a moderate increases in NaCl and hydration load, but when these responses cannot adequately respond because of the delivery of impermeable ions or very high tonicity, removal of the challenges are affected by a stimulation of mucociliary transport.

Interaction between ion transporters and the mucociliary transport system in dog and baboon

To gain insight into the role of epithelial ion channels, pumps, and cotransporters in regulating airway water and mucociliary transport, we administered inhibitors of the Na+ channel (amiloride), 3Na-2K-adenosinetriphosphatase (acetylstrophanthidin), and Na-K-2Cl cotransporter (furosemide) to anesthetized dogs and/or baboons. Tracheal ciliary beat frequency was measured by using heterodyne laser light scattering. Tracheal mucus velocity (TMV) and bronchial mucociliary clearance (BMC) or lung mucociliary clearance were measured by using radioaerosols and nuclear imaging. Respiratory tract fluid output was collected by using a secretion-collecting endotracheal tube. In six dogs, amiloride aerosol -lung deposition, 96 +/- 11 microg (means +/- SE)- had minimal effect, whereas acetylstrophanthidin aerosol (lung deposition, 71 +/- 9 microg) increased BMC, and furosemide (40 mg iv) markedly increased TMV. In five baboons, TMV increased after iv furosemide administration (2 mg/kg) as well as by aerosol (lung deposition, 20 +/- 3 mg), coincident with increases in ciliary-mucus coupling from 11.5 +/- 0. 1 to 29.5 +/- 0.4 and 46.5 +/- 0.7 microm/beat, respectively. Furosemide also increased lung mucociliary clearance in baboons. In dogs, respiratory tract fluid output increased after intravenous furosemide from 2.2 +/- 0.5 to 6.8 +/- 1.7 mg/min. When combined with dry-air inhalation, furosemide failed to stimulate TMV and reversed the inhibition of BMC by dry air. Thus pharmacological manipulation of the Na-K-2Cl cotransporter and the 3Na-2K-adenosinetriphosphatase pump may provide increases of clinical relevance in airway hydration and mucociliary transport.

Nonsustained polymorphous ventricular tachycardia during amiodarone therapy for atrial fibrillation complicating cardiomyopathy. Management with intravenous magnesium sulfate

A case is presented in which amiodarone was administered to suppress paroxysmal atrial fibrillation in a patient with an idiopathic cardiomyopathy. Eleven days after initiation of therapy with amiodarone, the patient experienced syncope and was noted to have recurrent episodes of polymorphous ventricular tachycardia. The patient was hospitalized and treated with a bolus as well as continuous infusion of intravenous magnesium sulfate. When the infusion was transiently discontinued, recurrences of polymorphous ventricular tachycardia were noted. The probable proarrhythmic action of amiodarone, although rare, is reviewed along with a discussion of the novel use of intravenous magnesium sulfate therapy.

Predictors of long-term survival in patients with malignant ventricular arrhythmias

The study consisted of 369 patients (age 62 +/- 13 years) who presented to our institution from April 1984 to April 1994 for malignant ventricular arrhythmias presenting as sustained ventricular tachycardia (VT) in 57% of patients, ventricular fibrillation in 25% of patients, and syncope due to VT in 17% of patients. Coronary artery disease was present in 74% of patients, cardiomyopathy in 19% of patients, and no evident heart disease in 7% of patients. Two hundred twenty-one patients were given drug, therapy, 47 patients underwent arrhythmia surgery, and 75 patients had an implantable cardioverter-defibrillator (ICD). During a mean follow-up of 30 months (range 1 to 101), 66 patients (18%) died from a cardiac death of which 26 (39%) were sudden. Cox regression analysis was conducted utilizing a total of 19 variables (clinical and therapeutic) in the entire population and separately in patients with coronary artery disease and cardiomyopathy. The most significant variables (multivariate analysis) of survival from cardiac mortality in the entire population were: congestive heart failure (CHF) class (p = 0.0003), ejection fraction (p = 0.02), and the use of drug therapy (p = 0.03); in patients with coronary artery disease, CHF class (p = 0.0001) and ejection fraction (p = 0.0006); and in patients with cardiomyopathy, CHF class (p = 0.009) and sustained VT on Holter monitoring (p = 0.007). Kaplan-Meier survival rates from cardiac death were: significantly lower (p = 0.005) in patients with CHF class III and IV compared with CHF class I and II (25% vs 58%, p = 0.005) with drug therapy; marginally significant (47% vs 88%, p = 0.06) from 20 to 40 months in patients with an ICD; and nonsignificant in patients who underwent arrhythmia surgery (63% vs 71%). Patients with an ICD had a better expected survival (82%) than patients who had arrhythmia surgery (69%) and drug therapy (65%). Thus, in patients with malignant ventricular arrhythmias, CHF class was the most significant independent predictor of survival from cardiac mortality over all disease substrates, and therapy influenced survival depending on the CHF class. Patients in CHF class III and IV who underwent arrhythmia surgery or had an ICD had a better expected survival than those taking drug therapy, and the negative impact of antiarrhythmic therapy was most prominent in patients with CHF class III and IV.

Syncope: the diagnostic value of head-up tilt testing

To determine the usefulness of prolonged head-up tilt in the diagnosis of neurally mediated syncope, 201 patients with history of syncope of unknown cause and 102 age and gender matched control subjects underwent a 40 minute 60 degrees head-up tilt test. Head-up tilt elicited syncope (i.e., was positive) in 74 of the 201 patients (37%) with a history of unexplained syncope and in only 6 of the 102 controls (6%). The specificity of the test was 100% in patients 60 years of age and older. Symptoms during tilt-induced syncope were identified by the patients as similar to those they had suffered during their spontaneous episodes. All 80 subjects who had tilt-induced syncope recovered without sequelae. The positive predictive value of a positive responses to head-up tilt was 93% and the negative predictive value was 43%. The results indicate that the prolonged head-up tilt test is a very specific procedure of high diagnostic value in patients with a history of unexplained syncope. It is particularly useful in the elderly age groups who have a high incidence of syncope.

Setting of relatively low energy outputs may permit implantation of a nonthoracotomy automatic cardioverter defibrillator system when high energy outputs prove ineffective

At intraoperative testing of defibrillation thresholds during implantation of internal cardioverter defibrillators, standard step-down approaches of energy outputs are used. If relatively high energy outputs are not successful at defibrillating the heart, the electrodes are frequently reconfigured. When attempting implantation of a nonthoracotomy lead system, high defibrillation thresholds may warrant opening of the chest cavity to place one or more epicardial electrodes. A case is presented where a nonthoracotomy system was able to be implanted using relatively low energy outputs which were reproducibly successful at terminating ventricular fibrillation when higher energy outputs were unsuccessful. Mechanisms for this phenomenon and alternate recommendations for defibrillation testing are presented.

Obstructive sleep apnea-induced supraventricular tachycardia

Obstructive sleep apnea has been associated with various cardiac arrhythmias; however, supraventricular tachycardia has not been reported to occur in this disorder. This case report describes a patient who developed episodes of supraventricular tachycardia during periods of apnea and oxygen desaturation. With the initiation of nasal continuous positive airway pressure during sleep, the arrhythmia was abolished. The etiology and possible mechanisms responsible for the supraventricular tachycardia are discussed.

Successful catheter ablation of an inferoseptal accessory pathway within the coronary sinus in a patient with a previously unsuccessful attempt at surgical interruption. Coronary sinus ablation for Wolff-Parkinson-White syndrome

In a patient with Wolff-Parkinson-White syndrome and a right inferoseptal accessory pathway who had had a previously unsuccessful surgical attempt at accessory pathway ablation, the accessory pathway was found to be adjacent to a branch of the coronary sinus. Radiofrequency energy was delivered within this branch to ablate the pathway successfully. This demonstrates an alternative approach to the more common method of radiofrequency ablation of accessory pathways from a tricuspid or mitral annular location.

Complete atrioventricular block with ventricular asystole following infusion of intravenous phenytoin

A case of complete atrioventricular block with ventricular asystole in a patient receiving intravenous phenytoin is presented. Although the potential for hypotension is generally recognized with the intravenous administration of phenytoin, conduction abnormalities are rarely reported. The differential diagnosis of atrioventricular block and the effects of phenytoin on cardiac conduction are discussed.

Flecainide induced atrial tachycardia with 1:1 ventricular conduction during exercise testing

Wide complex tachycardias may represent a rare proarrhythmic effect of some antiarrhythmic agents. The authors describe a patient who developed a wide complex tachycardia developing during stress testing while on therapy with flecainide, and the difficulty in interpreting the electrocardiogram. This article reviews potential proarrhythmic effects of flecainide in the treatment of atrial dysrhythmias and the difficulty in differentiating associated wide complex tachycardias.

Determinants of induction of ventricular tachycardia in nonsustained ventricular tachycardia after myocardial infarction and the usefulness of the signal-averaged electrocardiogram

Assessment of the implications of clinical and noninvasive variables, including the results of signal-averaged electrocardiography, was performed > or = 3 weeks after myocardial infarction in 57 patients with nonsustained ventricular tachycardia (VT) who underwent programmed ventricular stimulation to guide antiarrhythmic therapy. The clinical and noninvasive parameters assessed included ages, left ventricular ejection fractions, sites of infarction, presence of akinetic or dyskinetic left ventricular segments, history of syncope, history of coronary artery bypass surgery, and presence or absence of late potentials from signal-averaged electrocardiography. Other than the presence of late potentials, no clinical or noninvasive parameters identified such persons with a significantly higher likelihood of inducible VT. When assessed as positive if 1 or more variables were abnormal, 16 of 16 (100%) patients with versus 17 of 41 without inducible VT had late potentials (p < 0.002). With more stringent criteria required (defined as prolongation of the QRS vector complex duration and low root-mean-square voltage of the terminal 40 ms of the vector complex) 8 of 16 patients (50%) with and 4 of 41 (10%) without inducible VT had late potentials recorded (p < 0.002). Thus, the signal-averaged electrocardiogram may enable identification of persons with nonsustained VT after myocardial infarction who are most likely to have VT induced at programmed ventricular stimulation.

Effect of oral sotalol on systemic hemodynamics and programmed electrical stimulation in patients with ventricular arrhythmias and structural heart disease

We explored the central hemodynamic responses to oral sotalol during dose titration in patients with ventricular arrhythmias who underwent programmed ventricular stimulation. Twelve patients were included in the study, 9 with a history of sustained ventricular tachyarrhythmias (6 postmyocardial infarction and 3 with cardiomyopathy) and 3 with a history of nonsustained ventricular tachycardia postmyocardial infarction. Left ventricular ejection fractions were < 45% in 10 patients, and < 35% in 5; the mean ejection fraction was 37% (range 20-51%). Sotalol prevented the induction of ventricular tachycardia in each of 3 patients with nonsustained ventricular tachycardia and in 6 of 9 with sustained ventricular tachycardia at baseline study. At peak action (2 hours) after sotalol loading (mean dose, 167 mg orally twice daily), the hemodynamic effects included bradycardia, decreased cardiac index, increased left ventricular filling pressure and systemic vascular resistance, and no change in stroke volume or stroke work index. One patient was not continued on sotalol, owing to an excessive increase in the pulmonary capillary wedge pressure, despite the lack of symptomatic heart failure. Congestive heart failure in association with marked bradycardia developed in another patient, who had suppression of inducible ventricular tachycardia after sotalol loading; this patient was managed with a reduction in the dose of sotalol and a regimen of digoxin and furosemide, and has been well compensated and without a recurrence of sustained ventricular tachycardia for more than 4 years. Ventricular tachycardia has been controlled with sotalol, without hemodynamic deterioration, in 6 of these patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Identification of patients with high risk of arrhythmic mortality. Role of ambulatory monitoring, signal-averaged ECG, and heart rate variability

This article discusses the roles of 24-hour ambulatory Holter monitoring, left ventricular function, the signal-averaged electrocardiogram (ECG), and heart rate variability for identification of high risk patients following myocardial infarction. Because these noninvasive tests have low positive predictive value, a combination of noninvasive tests is recommended for risk stratification.

Hypersensitivity reaction associated with acute hepatic dysfunction following a single intravenous dose of procainamide

Rare cases of hepatotoxicity have been attributed to the antiarrhythmic agent procainamide. We here describe the case of a patient who had a hypersensitivity reaction to procainamide with fever, chills, arthralgia, abdominal pain and acute elevations of serum aminotransferase activities and bilirubin concentration. The reaction occurred after the patient had received a large intravenous dose during cardiac electrophysiological testing. This case should alert physicians to potential hepatotoxic reactions to procainamide, particularly with the increasing popularity of cardiac electrophysiological testing, during which this drug is commonly used.

Determinants of pace-terminable ventricular tachycardia: implications for implantable antitachycardia devices

The next generation of implantable antitachycardia devices incorporate antitachycardia pacing for the treatment of ventricular tachycardia. To evaluate the potential determinants of pace terminability, we analyzed 62 episodes of induced monomorphic ventricular tachycardia. We found that the tachycardia cycle length and cycle length variability are the major determinants of pace terminability. These findings should be considered in the designing of ventricular tachycardia detection and termination algorithms.

Sustained ventricular tachycardia associated with sarcoidosis: assessment of the underlying cardiac anatomy and the prospective utility of programmed ventricular stimulation, drug therapy and an implantable antitachycardia device

The presentation, cardiac anatomy and utility of programmed ventricular stimulation in seven patients with sustained ventricular tachycardia associated with sarcoidosis are described. The mean patient age was 38 +/- 8 years. Pulmonary involvement was apparent in three patients and no systemic manifestations of sarcoidosis were present in one patient. All patients had electrocardiographic abnormalities at rest and six had a left ventricular ejection fraction less than 45%. All seven patients had left ventricular wall motion abnormalities and five had mitral valve dysfunction. Sustained ventricular tachycardia was easily induced in all patients. Spontaneous sustained ventricular tachycardia was not prevented with corticosteroid administration. Despite antiarrhythmic drug therapy, two patients had sudden cardiac death and an additional four had recurrence of ventricular tachycardia. Four patients had an automatic cardioverter-defibrillator implanted and received drug therapy; all four received appropriate shocks. This report represents the largest descriptive series of consecutive patients with sustained ventricular tachycardia associated with sarcoidosis. Antiarrhythmic drug therapy of ventricular tachycardia in patients with sarcoidosis, even when guided with programmed ventricular stimulation, is associated with a high rate of arrhythmia recurrence or sudden death, or both. Thus, implantation of an automatic antitachycardia device (cardioverter-defibrillator) should be considered as primary therapy in such patients. Furthermore, sarcoidosis should be excluded, with Kveim skin testing if necessary, in any patient with sustained ventricular tachycardia of unknown origin.

The role of silent ischemia, the arrhythmic substrate and the short-long sequence in the genesis of sudden cardiac death

To study the role of silent ischemia and the arrhythmic substrate in the genesis of sudden cardiac death, 67 patients were studied (mean age 62 +/- 12 years). Of these, 14 patients (Group 1) had an in-hospital episode of ventricular tachycardia or fibrillation while wearing a 24 h Holter ambulatory electrocardiographic (ECG) monitor, 33 (Group II) had a documented episode of sustained ventricular tachycardia or fibrillation, or both, and 20 (Group III) had angina pectoris but no ventricular tachycardia or fibrillation. Eight Group I survivors underwent programmed electrical stimulation or ECG signal averaging, or both. All Group II patients underwent 24 h Holter monitoring and ECG signal averaging to detect late potentials before programmed electrical stimulation. Group III patients underwent both 24 h Holter recording and coronary angiography. The 24 h ECG tapes were analyzed for ST segment changes, prematurity index and characteristics of ventricular premature depolarizations. Any ST depression greater than or equal to 1 mm for greater than 30 s was considered to be a reflection of silent ischemia, and the induction of ventricular tachycardia or fibrillation by programmed electrical stimulation or the presence of late potentials, or both, was considered to be a reflection of the arrhythmia substrate. Silent ischemia preceded ventricular tachycardia in only 2 (14%) of the 14 Group I patients. The prematurity index was less than 1 in only 18% of ventricular tachycardia episodes.(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiopulmonary resuscitation: qualifications and performance of housestaff and trained internists

Eighty-six physicians in the Internal Medicine Department of the Mount Sinai Medical Center were evaluated on attitudes and knowledge of basic and advanced cardiac life support. Information was gathered over a one-week period using a self-administered questionnaire. Eighteen (21%) of the respondents did not know of the availability of basic and advanced cardiac life support courses at this institution. Of the physicians who had never taken either course, 8 (25%) stated it was because it was not offered at a convenient time or place. All housestaff officers were noted to have completed both courses, a percentage much higher than that of the trained internists (p less than .0001). Previous formal training in cardiac life support was found to be associated with a higher level of confidence in the ability to administer cardiac lifesaving techniques (p less than .0001) and a higher overall knowledge score (p = .003). We determined that the housestaff officers in internal medicine were the physicians most qualified to perform resuscitation efforts because of their completion of life support courses, their confidence in administering these techniques, and their greater overall knowledge. Wider publicity on the availability of cardiac life support courses, more convenient scheduling of such courses, and mandatory certification in basic life support for all physicians, with additional certification in advanced cardiac life support for physicians with extensive ward responsibility, are needed.

The prognostic significance of quantitative signal-averaged variables relative to clinical variables, site of myocardial infarction, ejection fraction and ventricular premature beats: a prospective study

A prospective study was undertaken of the prognostic significance of quantitative signal-averaged electrocardiographic (ECG) variables relative to clinical variables, site of myocardial infarction, left ventricular ejection fraction and characteristics of ventricular premature beats in 115 patients (mean age 62 +/- 12 years) studied 10 +/- 6 days after myocardial infarction. Signal-averaged variables included the root mean square voltage of the terminal 40 ms, the duration of the filtered signal-averaged QRS complex and low amplitude signals less than 40 microV determined at 25 and 40 Hz high pass filtering in all patients. Of the 115 patients, 51 (44%) had an abnormal signal-averaged ECG (one or more abnormal signal-averaged variables), 51 (44%) at 25 Hz and 48 (42%) at 40 Hz high pass filtering. A higher proportion of patients with an inferior wall infarction had an abnormal signal-averaged ECG as compared with patients with anterior wall infarction (58% versus 31%). Over a 14 +/- 8 month follow-up period 16 patients (14%) had an arrhythmic event. An abnormal signal-averaged ECG at 40 Hz high pass filtering had a higher sensitivity (81% versus 75%) and specificity (65% versus 61%) than at 25 Hz high pass filtering. The predictive value of the signal-averaged ECG was superior to that of the ejection fraction (40% versus 20%) in anterior wall myocardial infarction, whereas in patients with inferior wall infarction, the predictive values of the two tests were equivalent. The prognostic power of 27 clinical and noninvasive variables was determined with the Cox proportional hazards regression model.(ABSTRACT TRUNCATED AT 250 WORDS)

Role of signal averaging of the surface QRS complex in selecting patients with nonsustained ventricular tachycardia and high grade ventricular arrhythmias for programmed ventricular stimulation

Signal averaging of the surface QRS complex was performed before programmed ventricular stimulation in 53 individuals with high grade ventricular arrhythmias or nonsustained ventricular tachycardia, or both. An abnormal signal-averaged electrocardiogram (ECG) was recorded in 22 patients and was associated with inducible ventricular tachycardia in 12 (55%) of the 22. In contrast, a normal signal-average ECG was associated with inducible tachycardia in only 1 (3%) of 31 individuals (p less than 0.005). The group with inducible tachycardia had a longer duration of the signal-averaged QRS complex (124 +/- 19 versus 96 +/- 26 ms) and of low amplitude signals (44 +/- 13 versus 29 +/- 11 ms) (p less than 0.005). In addition, the root mean square voltage of the terminal 40 ms was lower in this group (20 +/- 14 versus 48 +/- 34 microV, p less than 0.005). Twenty-seven of the 53 subjects had a prior myocardial infarction; 17 (63%) of the 27 had an abnormal signal-averaged ECG, and ventricular tachycardia was inducible in 10 (59%) of the 17. A normal signal-averaged ECG was recorded in 10 of the 27 patients and only 1 (10%) of these 10 had inducible tachycardia. An abnormal signal-averaged ECG had a 91% sensitivity and a 56% specificity with respect to subsequent induction of tachycardia. During long-term follow-up, 2 (15%) of the 13 patients with inducible ventricular tachycardia who were treated with electrophysiologically guided antiarrhythmics therapy died suddenly; the remaining 11 patients (85%) are alive 15 +/- 10 months after electrophysiologic testing.(ABSTRACT TRUNCATED AT 250 WORDS)

A comparative analysis of signal averaging of the surface QRS complex and signal averaging of intracardiac and epicardial recordings in patients with ventricular tachycardia

To test the hypothesis that late potentials may be more enhanced by signal processing of intracardiac and epicardial electrograms, we performed a comparative analysis of signal averaging (SA) of the surface QRS complex (method I), signal averaging of an endocardial electrode catheter recording (method II), and epicardial recording (method III) in 24 patients (mean age = 55 +/- 14 years). Sixteen of the 24 patients (66%) had spontaneous as well as induced sustained ventricular tachycardia (VT), whereas the remaining 8 patients (33%) had spontaneous non-sustained VT. SA by the three methods was performed within less than or equal to 24 hours of each other, utilizing a band pass filter frequency of 25 to 250 Hz. The duration of the SA-QRS complex, low amplitude signals (LAS) of less than 40 microV and the RMS-voltage (V) of the terminal 40 ms were determined for the three methods. There was a significant correlation between method I and methods II and III for the SA-QRS duration (r = .928, p less than .001), RMS-V (r = .634, p less than .002) and LAS (r = .783, p less than .001). There was no significant difference in the quantitative signal-averaged parameters between the three methods. The incidence of the RMS-V of less than 25 microV (37.5% vs 21%); LAS of greater than 32 ms (46% vs 37.5%) and SA-QRS of greater than 120 ms (54% vs 42%) was higher but statistically non-significant by methods II and III when compared to method I. We concluded that: (1) SA of intracardiac electrograms correlate well with SA of the surface QRS. This observation further validates the technique of surface SA to detect delayed ventricular activation. (2) SA of intracardiac electrograms may provide additional information on quantitative SA parameters relative to surface QRS in some patients with VT.