Prognostic significance of 24 hour ambulatory electrocardiographic monitoring in patients with hypertrophic cardiomyopathy: A prospective study

The prevalence and prognostic significance of ventricular arrhythmias identified on 24 hour ambulatory electrocardiographic monitoring was prospectlvely assessed in 99 patients with hypertrophie cardiomyopathy. In the absence of antlarrhythmic therapy, high grade ventricular arrhythmias (grade 3 and above) were common; that is, they were identified in 66 percent of the patients, including 19 percent with episodes of asymptomatic ventricular tachycardia.Clinical outcome was assessed 3 years after the initial 24 hour ambulatory electrocardiogram. Of the 84 patients who did not undergo ventricular septal myotomy-myectomy, 6 died suddenly or experienced cardiac arrest, 1 died of progressive congestive heart failure and the other 77 have survived without a cardiac catastrophe. The prevalence rate of sudden death or cardiac arrest during the follow-up period was the same (3 percent) in patients with high grade arrhythmias other than ventricular tachycardia (1 of 37) as in those with no or low grade arrhythmias (1 of 29). However, the occurrence of a sudden cardiac catastrophe was significantly more common in patients with asymptomatic ventricular tachycardia of brief duration on 24 hour electrocardiography (4 [24 percent] of 17) than in patients without ventricular tachycardia (2 [3 percent] of 66) (p <0.02).In summary, (1) high grade ventricular arrhythmias are commonly found on continuous 24 hour electrocardiographic monitoring in patients with hypertrophic cardiomyopathy; and (2) although sudden death is relatively uncommon in patients with high grade ventricular arrhythmias other than ventricular tachycardia (annual mortality rate 1 percent), the finding of ventricular tachycardia on 24 hour electrocardlography identifies a subgroup of patients at high risk for sudden death (annual mortality rate 8.6 percent). Although no conclusions can be drawn regarding the impact of therapy, our findings suggest that 24 hour electrocardiographic monitoring should be performed in patients with hypertrophic cardiomyopathy and that it may be reasonable to initiate antlarrhythmic therapy if ventricular tachycardia is identified.     

Adenosine‐Induced Ventricular Arrhythmias in Patients with Supraventricular Tachycardias

Background: Adenosine is widely used for the diagnosis and the termination of supraventricular arrhythmias. There are many case reports and few series about the proarrhythmic potential of adenosine. We sought to evaluate the proarrhythmic potential of adenosine used to terminate the supraventricular arrhythmias. Methods: The records of all patients that received adenosine for the termination of supraventricular tachycardia were reviewed retrospectively and those with a continuous electrocardiographic (ECG) recording during adenosine administration were included to the study. Results: Our search identified 52 supraventricular episodes of 46 patients with a continuous ECG recording during adenosine administration. Following adenosine administration, premature ventricular contraction (PVC) or ventricular tachycardia (VT) developed in 22 (47.8%) patients and in 26 (50%) tachycardia episodes. No patient had a sustained VT. Nonsustained VT developed in eight (17.4%) patients. All VT episodes were polymorphic, short, and self‐terminating. When the basal and demographic properties of patients with PVC or VT and those without PVT or VT were compared, there was no significant difference. Conclusions: Adenosine is a quite safe and effective drug for the termination of narrow QRS complex tachycardia but it often induces nonsustained VT or PVC that are clinically insignificant in the absence of other accompanying heart disease.     

Variability of ventricular arrhythmias in hypertrophic cardiomyopathy and implications for treatment

Asymptomatic ventricular arrhythmias are common in patients with hypertrophic cardiomyopathy (HC) and are associated with sudden death. The variability of ventricular extrasystoles and optimal duration of electrocardiographic (ECG) monitoring necessary to exclude ventricular tachycardia (VT) were assessed in 16 patients with HC in whom VT was detected during the first 48 hours of ECG monitoring. One hundred eight episodes of VT (range 0 to 10, mean 1.5 per day) were recorded (52% incidence) during 48 to 168 hours of ECG monitoring (median 72) without cardiac medication within a 1-year period. The likelihood of excluding VT on K days of ECG monitoring was determined. The probability of failing to detect VT in our selected group was 48% for 24 hours of ECG monitoring, 23% for 48 hours and 11% for 72 hours. Daily ventricular extrasystole rates were 2 to 17,693 (median 187). Analysis of variance, applied to 10 patients with enough ventricular extrasystoles for analysis, indicated that a 61% reduction of ventricular extrasystoles in consecutive 24-hour periods was necessary to attribute an effect to the intervention rather than to spontaneous variability with 95% confidence. A sine wave curve fitted to the ventricular extrasystole counts revealed a circadian rhythm with a night frequency peak in 5 patients and an afternoon peak in 5. Thus, 48- to 72-hour ECG monitoring represents a pragmatic compromise in assessing drug intervention once VT is detected;longer periods (5 to 6 days) of ECG monitoring are required to exclude VT at initial evaluation, although the prognostic significance of VT detected after the first 72 hours is uncertain.(ABSTRACT TRUNCATED AT 250 WORDS)     

Ventricular arrhythmias in postoperative tetralogy of Fallot.

Ventricular arrhythmias in patients after total surgical repair of tetralogy of Fallot have been associated with late sudden death. In this large multicenter retrospective study of 359 patients with postoperative tetralogy of Fallot, spontaneous ventricular premature complexes (VPCs) on 24-hour ambulatory electrocardiographic monitoring and laboratory-induced ventricular tachycardia (VT) by electrophysiologic stimulation were analyzed. The mean age at surgical repair was 5 years and the mean follow-up duration after repair was 7 years. Spontaneous VPCs on ambulatory monitoring were found in 48% and induced VT on electrophysiologic stimulation was found in 17% of patients. Both spontaneous VPCs and induced VT were significantly related to delayed age at repair, longer follow-up interval, symptoms of syncope or presyncope and right ventricular systolic hypertension (greater than 60 mm Hg) (p less than 0.05), but not to right ventricular diastolic pressure greater than 8 mm Hg. The VPCs on ambulatory monitoring were more complex with increasing age at repair and follow-up duration. Induction of VT on electrophysiologic stimulation correlated with spontaneous VPCs including VT on 24-hour ambulatory electrocardiographic monitoring. The electrophysiologic stimulation protocol varied and the induction of VT increased with a more aggressive stimulation protocol. While induced sustained monomorphic VT was related to all forms of spontaneous VPCs, induced nonsustained polymorphic VT was related to more complex forms of VPCs on ambulatory monitoring. VT was not induced in asymptomatic patients who had normal 24-hour ambulatory electrocardiographic monitoring and normal right ventricular systolic pressure. (ABSTRACT TRUNCATED AT 250 WORDS)     

Myocardial ischemia and ventricular tachycardia on continuous electrocardiographic monitoring and risk of cardiovascular outcomes after non-ST-segment elevation acute coronary syndrome (from the MERLIN-TIMI 36 Trial)

Among patients with non-ST-segment elevation acute coronary syndromes, recurrent ischemia and ventricular arrhythmias detected on continuous electrocardiographic monitoring remain common events that are associated with worse outcomes. The relative clinical significance of both events together is not well described. We determined the risk associated with ischemia (≥1 mm ST depression lasting ≥1 minutes) and ventricular tachycardia (VT) (≥4 beats) detected on 7-day continuous electrocardiographic monitoring in 6,355 patients with non-ST-segment elevation acute coronary syndromes from the Metabolic Efficiency with Ranolazine for Less Ischemia in Non-ST-elevation Acute Coronary Syndrome-Thrombolysis In Myocardial Infarction (MERLIN-TIMI) 36 trial. The patients were categorized into 4 groups according to the presence or absence of VT and ischemia. Cardiovascular death, sudden cardiac death (SCD), myocardial infarction, and recurrent ischemia were assessed during a median follow-up of 348 days. A total of 60.0% patients had no VT or ischemia, 20.0% had VT alone, 14.7% had ischemia alone, and 5.3% had both. The patients with either VT or ischemia were at increased risk of cardiovascular outcomes. The combination of ischemia and VT identified a particularly high-risk population for cardiovascular death (10.1% vs 3.0%, p <0.001), SCD (7.8% vs 0.9%, p <0.001), and myocardial infarction (15.4% vs 6.2%, p <0.001) compared to patients with neither. The addition of arrhythmia and ischemia significantly improved the clinical model for predicting cardiovascular death or SCD (p <0.001). In patients with both ischemia and VT, 66.6% of SCD occurred within 90 days of the non-ST-segment elevation acute coronary syndromes. In conclusion, in >6,300 patients with non-ST-segment elevation acute coronary syndromes, the presence of myocardial ischemia or VT alone, and particularly in combination, was independently associated with poor cardiovascular outcomes and thus provides incremental improvement in early risk stratification.     

Hypertrophic myocardiopathy (II). 24-hour electrocardiographic monitoring and its relation to the echocardiographic characteristics

Seventy-two patients with hypertrophic cardiomyopathy were evaluated by 24 hours of electrocardiographic ambulatory monitoring. The results were related to echocardiographic extent of hypertrophy, left ventricular outflow obstruction at rest, and transmitral flow parameters. Also, the symptoms and functional classification of NYHA were related to ventricular arrhythmias. Ventricular arrhythmias were detected in 68% of our patients: high degree of ventricular ectopia in 26 (36.1%), and ventricular tachycardia in 14 (19.4%). Most important supraventricular arrhythmias were: atrial fibrillation in 7 patients, atrial flutter in one, and supraventricular tachycardia in five. Asymmetric hypertrophy type I of Maron classification showed the lower number of ventricular arrhythmias. High degree of ventricular arrhythmias were more frequent in patients with: apical hypertrophy, worse functional classification of NYHA (I: 20%; II: 50%; III: 80%), and in patients with impaired distensibility detected by Doppler (80.7% vs 56.7%; p less than 0.05). There was no relationship between left ventricular outflow obstruction at rest and ventricular arrhythmias.     

Diltiazem in paroxysmal supraventricular tachycardia: electrocardiographic findings at termination]

The effects of diltiazem hydrochloride (0.3 mg/kg i.v. over 2 min.) was studied by continuous electrocardiographic monitoring in 60 patients. Conversion to sinus rhythm was achieved in 55 patients (91%). Electrocardiographic findings were: undisturbed sinus rhythm in 20 patients; A-V junctional rhythm in 4 patients; complex ventricular arrhythmias (ventricular tachycardia or complex VPCs) in 19 patients. Patients with complex ventricular arrhythmias were matched against patients with normal sinus rhythm, with respect to the following parameters: age, sex, heart disease, tachycardia duration, tachycardia cycle length, sinus cycle length, pre- and post-infusion blood pressure. No differences between the two groups of patients were found. Ventricular arrhythmias occurring at the termination of supraventricular tachycardia are difficult to explain. Nevertheless, these arrhythmias are not associated with organic heart disease. They could be the expression of triggered activity.     

Programmed ventricular stimulation in mitral valve prolapse: analysis of 36 patients

Programmed ventricular stimulation with 3 extrastimuli was performed in 36 patients with mitral valve prolapse (MVP). Among 11 patients without transient cerebral symptoms, none had inducible ventricular tachycardia (VT) or ventricular fibrillation (VF), whether or not nonsustained VT or ventricular premature complexes (VPC) were present during ambulatory electrocardiographic recordings. These patients remained well without antiarrhythmic drug therapy for 6 to 57 months (mean 23) of follow-up. Two patients with recurrent unexplained syncope and no documented ventricular arrhythmia during electrocardiographic monitoring also had no inducible VT or VF. Among 20 patients with syncope or presyncope and documented nonsustained VT or VPCs during electrocardiographic monitoring, polymorphic nonsustained VT was induced in 8, sustained unimorphic VT in 2, and VF in 3. In 1 patient who had inducible polymorphic nonsustained VT, electrocardiographic monitoring during syncope showed sinus rhythm. Among 3 patients with a history of sustained VT or VF, unimorphic VT was induced in each. Patients with MVP who have asymptomatic ventricular ectopic activity and no inducible VT may have a benign prognosis without treatment. In patients who have transient cerebral symptoms and documented nonsustained VT or VPCs, VT or VF is inducible in 65%, most often polymorphic VT. It is unclear in which patients this finding is clinically significant and in which it is a nonspecific response to programmed stimulation.     

Continuous electrocardiographic monitoring in patients with sickle-cell anemia during pain crisis

Electrocardiographic studies in patients with sickle-cell anemia have been performed during the normal resting state with routine twelve-lead ECGs. We studied 30 patients with sickle-cell disease in acute crisis with 24-hour continuous electrocardiographic monitoring. The standard ECG demonstrated a high incidence of abnormalities, but only three patients had arrhythmias. These findings contrasted sharply with the results of continuous monitoring, during which arrhythmias were detected in 24 of 30 patients. They were fairly evenly split between atrial (60%) and ventricular (67%). Nine of the patients had “complex arrhythmias” including two with episodes of ventricular tachycardia. Seventeen patients subsequently underwent equilibrium gated-blood pool scans. Eight patients had abnormal contractility and tended to have more arrhythmias on monitoring than those with normal contractility. Thus, continuous electrocardiographic monitoring of sickle-cell patients during crisis revealed a higher incidence of arrhythmias than previously thought.     

Correlation of various types of perfusion defects with supraventricular and ventricular arrhythmias in hypertrophic cardiomyopathy

To ascertain the relationship between the types of myocardial perfusion defects and supraventricular and ventricular tachyarrhythmias in hypertrophic cardiomyopathy (HCM), 26 patients were studied with dipyridamole-loading thallium-201 scintigraphy and the results were correlated with 24-hour ambulatory ECG, echocardiograms and hemodynamic data. Myocardial perfusion defects were detected in 10 of the 26 patients (38%); three with large defects (LD) and seven with multiple small defects (SD). The patients with defects had greater degree of asymmetric septal hypertrophy (1.82 +/- 0.49 vs 1.27 +/- 0.38, p less than 0.01) and lower cardiac indices (2.35 +/- 0.31 vs 2.70 +/- 0.43, p less than 0.05) than did the patients without defects. Paroxysmal atrial fibrillation (PAf) and/or paroxysmal supraventricular tachycardia (PSVT) were observed in six of the 10 patients with defects (60%) and in four of the 16 patients without defects (25%). Ventricular tachycardia (VT) was identified in six of the 10 patients with defects (60%) but in only three of the 16 patients without defects (19%) (p less than 0.05). Among 10 patients with defects, PAf and/or PSVT were present in six of the seven patients with SD, but not in any of the patients with LD (p less than 0.05). VT was present in five of the seven patients with SD and in one of the three patients with LD. In conclusion, 1) perfusion defects in HCM are associated with greater degree of asymmetric septal hypertrophy, the lower cardiac indices, and higher prevalences of PAf, PSVT and VT; 2) Perfusion defects can be classified in two types; ie., multiple small defects and large defects; 3) Patients with multiple small defects commonly have PAf, PSVT as well as VT. This correlation may be of clinical importance, particularly in evaluating the causes of the defects and mechanisms of these arrhythmias.     

Long-duration electrocardiographic recording in 33 patients with obstructive cardiomyopathy

A prospective study of arrhythmias was performed in 33 patients with hypertrophic cardiomyopathy with obstruction by Holter monitoring. The aim of the study was to assess the incidence of "occult" arrhythmias in this condition and to establish a "profile" of high risk patients from clinical, echocardiographic and haemodynamic data. The Holter monitoring demonstrated asymptomatic arrhythmias in 31 of the 33 patients (94%). A supraventricular arrhythmia was detected in 15 cases (45%), including 7 episodes of supraventricular tachycardia (21%). Ventricular arrhythmias were observed in 28 patients (85%), including 5 episodes of ventricular tachycardia (15%). Some patients presented several types of arrhythmia. A number of patients with arrhythmia including short bursts of ventricular tachycardia were asymptomatic during Holter monitoring; conversely, other patients complained of dizziness or syncope but had no arrhythmias. A retrospective study of clinical, echocardiographic and haemodynamic data showed no difference between patients with and patients without arrhythmias. Medium-dose betablocker therapy (propranolol, 110 mg/day) did not seem to protect patients with hypertrophic cardiomyopathy with obstruction from arrhythmias. We conclude that Holter monitoring should form part of the routine evaluation of patients with cardiomyopathy with obstruction, and that potentially dangerous arrhythmias should be treated by anti-arrhythmic agents other than betablockers. This attitude could reduce the incidence of syncope and eventually decrease the risk of sudden death in this condition.     

Sustained ventricular tachycardia responsive to verapamil in patients with hypertrophic cardiomyopathy. Clinical and electrophysiological assessment of drug efficacy

Recently, we examined 2 cases of hypertrophic cardiomyopathy (HCM) presenting with sustained ventricular tachycardia (VT). One case was a 62 year old male with midventricular hypertrophy and monomorphic sustained VT. After admission, the efficacies of procainamide, disopyramide, aprindin, flecainide, mexiletine and verapamil were evaluated by means of continuous electrocardiographic monitoring. Verapamil prevented the recurrence of sustained VT and markedly reduced the frequency and number of runs of nonsustained VT. In the electrophysiologic study, rapid VT was induced by double extrastimuli at the right ventricular apex. Intravenous verapamil at a dose of 10 mg prevented the induction of VT. The patient was discharged on verapamil and remains asymptomatic after 3 months of follow up. The other case was a 34 year old female who was a survivor of cardiac arrest. Monomorphic VT was observed on emergency admission and was converted to sinus rhythm by direct current cardioversion after resuscitation. In the electrophysiologic study, rapid VT was induced by double extrastimuli at the right ventricular outflow tract. Verapamil at a dose of 10 mg prevented the induction of VT. These 2 cases of HCM are rare in that they presented with sustained VT. It is also of interest that verapamil, which has been used conventionally in HCM, prevented VT.     

Holter detection of cardiac arrhythmias in intracranial subarachnoid hemorrhage

To determine the frequency and severity of cardiac arrhythmias in intracranial subarachnoid hemorrhage, 120 nonselected patients were prospectively studied by 24-hour Holter monitoring. Arrhythmias were found in 96 of 107 patients (90%) with adequate Holter recording: ventricular premature complexes in 49, nonsustained ventricular tachycardia in 5, supraventricular premature complexes in 29, paroxysmal supraventricular tachycardia or atrial fibrillation in 9, sinoatrial block and arrest in 29, second-degree atrioventricular block in 1, atrioventricular dissociation in 4 and idioventricular rhythm in 2. Life-threatening ventricular arrhythmias (torsades de pointes-type ventricular tachycardia) occurred in 4 patients, degenerating into either ventricular flutter or fibrillation in 2. ST-segment changes suggestive of acute transitory myocardial ischemia were found in 8 patients (1.5 mm or more of ST depression in 7 patients and 1.5 mm or more of ST elevation in 1 patient). The frequency and severity of arrhythmias were significantly higher in patients studied within 48 hours of subarachnoid hemorrhage; serious ventricular arrhythmias were associated with QTc prolongation more than 550 ms and with hypokalemia less than 3.5 mEq/liter. No correlation was found between age, clinical condition, site and extent of subarachnoid hemorrhage and either the occurrence or severity of arrhythmias. The results of our study indicate an extremely high incidence of arrhythmias, sometimes serious, in subarachnoid hemorrhage, especially in the first 48 hours after hemorrhage. Continuous electrocardiographic monitoring is therefore mandatory.     

Prognostic significance of sustained monomorphic ventricular tachycardia induced by programmed ventricular stimulation using up to triple extrastimuli in survivors of acute myocardial infarction

The prognostic significance of sustained monomorphic ventricular tachycardia (VT) induced by programmed ventricular stimulation using up to 3 extrastimuli was evaluated in 133 consecutive survivors of acute myocardial infarction (AMI) at a mean interval of 1.8 +/- 1.1 months after onset. This was compared with hemodynamic and angiographic abnormalities shown by cardiac catheterization and ventricular ectopic activity detected by Holter monitoring. Sustained monomorphic VT was induced in 25 (19%) patients, sustained polymorphic VT in 11 (8%) patients, nonsustained monomorphic VT (greater than or equal to 10 beats) in 12 patients (9%) and nonsustained polymorphic VT in 9 patients (7%). Multivariate logistic regression analysis of clinical, angiographic, hemodynamic and electrocardiographic variables showed that the presence of a left ventricular aneurysm (p = 0.005) and Lown grade 4B ventricular ectopic activity (p less than 0.001) were independent predictors of inducibility of sustained monomorphic VT. During a mean follow-up of 21 +/- 13 months, there were 8 (6%) sudden cardiac deaths and 3 (2.3%) spontaneous occurrences of life-threatening sustained VT. The 2-year probability of freedom from sudden cardiac death or sustained ventricular tachyarrhythmias was 53 +/- 13% for patients with inducible sustained monomorphic VT, 70 +/- 10% for those with a left ventricular ejection fraction less than 40% and 58 +/- 13% for those with Lown grade 4B ventricular ectopic activity.(ABSTRACT TRUNCATED AT 250 WORDS)     

Arrhythmias in the mitral valve prolapse syndrome. Prevalence, nature, and frequency.

Ambulatory monitoring and maximal treadmill exercise were compared in 40 normal subjects and 31 patients with mitral prolapse. A variable arrhythmia spectrum was observed in prolapse during monitoring: premature ventricular contractions in 18 (58%), supraventricular arrhythmias in 11 (35%), and bradyarrhythmias in 9 (29%). Significantly less arrhythmias occurred in normal subjects during monitoring: 10 (25%, P greater than 0.001), 3 (8%, P less than 0.001), 4 (10%, P less than 0.05), and 2 (5%, P less than 0.02), respectively. In patients with prolapse, arrhythmias occurred on resting electrocardiogram (ECG), 35% premature ventricular contractons, 6% supraventricular arrhythmias, and 10% bradyarrhythmias, and on treadmill exercise, 45%, 10%, and 3%; therefore, ambulatory monitoring was the most sensitive method of arrhythmia detection. No correlation existed between clinical features of prolapse and arrhythmias. Thus, arrhythmias occur in most patients with mitral prolapse, are not predictable by clinical characteristics, comprise a spectrum of ventricular and supraventricular tachyarrhythmias and bradyarrhythmias, and are best detected by ambulatory ECG monitoring.     

Prognostic assessment of survivors of ventricular tachycardia and ventricular fibrillation with ambulatory monitoring

The ability to assess prognosis in patients with serious ventricular arrhythmias treated with antiarrhythmic drugs by the degree of complexity on the 24-hour ambulatory electrocardiogram was evaluated in 59 survivors of ventricular tachycardia (VT) and ventricular fibrillation. After conventional therapy had failed, patients were treated with investigational drugs until symptomatic VT was abolished. A Holter monitor recording, obtained once the therapeutic regimen was established, was graded for the presence or absence of asymptomatic VT. Fifty-two patients were asymptomatic at discharge and were followed for 700 days. Of 44 patients followed for 1 year, none had recurrent syncope or died if asymptomatic VT was absent at 1 month (p <0.002). After 700 days, 27 patients (82%) without asymptomatic VT at 1 month were doing well, compared with 11 patients (58%) with asymptomatic VT at 1 month (p <0.002). In patients at risk for sudden cardiac arrest, early abolition of asymptomatic VT on ambulatory monitoring can be used to predict a good long-term clinical response.     

Postoperative arrhythmias and risk factors after open heart surgery

Cardiac arrhythmias were recorded during 24 hours in 40 consecutive patients requiring open-heart surgery, using continuous Holter monitoring. Most patients developed both supraventricular and ventricular arrhythmias. Complex ventricular arrhythmias were detected in 31 patients (78%) and 2 patients suffered an immediate postoperative myocardial infarction. The following risk factors were considered: age, sex, type of heart disease, preoperative left ventricular ejection fraction, cardiopulmonary bypass and aortic clamping duration, length of anesthesia, dopamine administration, and maximal level of CK and CK-MB. Only dopamine administration, even in low renal dose, was associated with the number and severity of ventricular arrhythmias.     

Independent prognostic value of supraventricular arrhythmias on 24-h ambulatory monitoring following myocardial infarction.

To determine the prognostic value of supraventricular arrhythmias, in addition to ventricular arrhythmias and clinical variables after myocardial infarction, 99 consecutive patients had 24-h ambulatory monitoring within 2 weeks of discharge. All patients completed at least 4-year follow-up (mean 56 +/- 6 months). During follow-up there were 29 cardiac events (13 cardiac deaths and 16 reinfarctions). The highest risk was associated with ventricular tachycardia (positive predictive accuracy 100%, negative predictive accuracy 75%, risk ratio 4.0) and supraventricular tachycardia i.e. paroxysmal tachycardia or AV nodal tachycardia (positive predictive accuracy 86%, negative predictive accuracy 80%, risk ratio 4.2). By multivariate analysis, supraventricular tachycardia proved to be an independent predictive variable, in addition to ventricular tachycardia, premature ventricular depolarisations greater than or equal to 10 h-1 and the presence of Killip class greater than or equal to II while in the coronary care unit for future cardiac events. These data suggest that supraventricular tachycardias detected on 24-h ambulatory monitoring shortly after discharge carry a poor prognosis and may indicate a different pathophysiology as compared to ventricular tachycardias.     

Arrhythmia in hypertrophic cardiomyopathy: exercise and 48 hour ambulatory electrocardiographic assessment with and without beta adrenergic blocking therapy

Submaximal treadmill exercise electrocardiography and 48 hour ambulatory electrocardiographic monitoring were performed in 30 patients with hypertrophic cardiomyopathy both with and without beta adrenergic blocking therapy. During ambulatory electrocardiographic monitoring 1 patient (3 percent) had no arrhythmia, 14 patients (46 percent) had supraventricular tachycardia or paroxysmal atrial fibrillation, 13 (43 percent) had multiform or paired ventricular extrasystoles and 8 (26 percent) had ventricular tachycardia. The frequency of these ventricular arrhythmias was almost identical with and without beta adrenergic blocking drugs (mean dose in "propranolol equivalents" 280 mg daily). With beta blocking therapy fewer patients had supraventricular tachycardia; however, the difference was not significant. During exercise testing 18 patients (60 percent) had ventricular extrasystoles and 3 patients (10 percent) had paired ventricular extrasystoles and the frequency was almost identical with and without beta adrenergic blocking therapy. No routine echocardiographic or hemodynamic measurement predicted the serious ventricular arrhythmias. It is concluded that asymptomatic ventricular arrhythmia is a common occurrence in patients with hypertrophic cardiomyopathy and its frequency is not reduced with beta adrenergic blocking therapy. Because occult arrhythmia may be the cause of sudden death it is important to detect it in these patients so that an effort can be made to improve prognosis with specific antiarrhythmic treatment.     

Arrhythmias in hypertrophic cardiomyopathy. Significance and therapeutic consequences

The natural history of the patient with hypertrophic cardiomyopathy is characterized by slow progression of symptoms and left ventricular hypertrophy; severe functional limitation is unusual and encountered only in about 20%. Most of the deaths are sudden and occur irrespective of the functional status of the patient and there are no routine electrocardiographic or hemodynamic measurements indicative of poor prognosis. Sudden death may be associated with syncope and young age at diagnosis as well as with a family history of sudden death. The mechanisms underlying the cause of sudden death have not been clearly elucidated. Although complete heart block may complicate myotomy or myectomy, the development, in an unoperated patient, of symptomatic conduction disease is uncommon. Preexcitation syndromes may be present in a small subpopulation (about 2%), but this appears seldom responsible for sudden death. Outflow tract spasm has also been postulated as a causal factor but the fact that proportionately an equal number of patients with and without ventricular outflow gradients die suddenly, suggests that other mechanisms must be important. Further hypotheses, currently however, without substantiation, have implicated acute changes in diastolic filling or acute myocardial ischemia as causes of sudden death. Recently published studies have stressed the importance of ventricular arrhythmias as a cause of sudden death. Ventricular tachycardia occurs in about 30% of such patients and can be found significantly more frequent in adult patients who die suddenly. In children and adolescents, since they have a lesser incidence of ventricular tachycardia, possibly, other mechanisms are involved. In general, episodes of ventricular tachycardia are asymptomatic and self-limited; the main ventricular rate recorded during 135 episodes in 30 of our patients was 142 beats per minute with an average duration of eight beats. Variable QRS morphology suggests different sites of origin. Due to the marked spontaneous variability, the probability of missing ventricular tachycardia with a single 24-hour continuous ambulatory ECG is 54%; on 96 hours of continuous ECG monitoring the probability can be reduced to 8%. Accordingly, continuous ambulatory ECG monitoring should be carried out for at least 48 to 72 hours. At the time of diagnosis, approximately 7% of the patients have atrial fibrillation. On three days of continuous 24-hour ECG monitoring, about 40% will be found to have atrial fibrillation or supraventricular arrhythmias. The correlation between supraventricular arrhythmias and sudden death is weaker than that of the latter with ventricular arrhythmias.(ABSTRACT TRUNCATED AT 400 WORDS)