Contribution of ambulatory electrocardiographic monitoring to antiarrhythmic management

Ventricular dysrhythmias in middle-aged hypertensive men treated either with a diuretic agent or a beta-blocker

The purpose of this study was to identify the frequency of cardiac dysrhythmias in two similar groups of hypertensive middle-aged males (age 45-66). They had previously been randomized either to a diuretic treatment (n = 42), or a beta-blocking agent (n = 41). A 24-hour ambulatory Holter monitoring, and serum potassium, was obtained in all patients, serum magnesium was measured in 35 patients. The mean number of ventricular premature beats (VPBs) and the frequency of complex arrhythmias (19 vs. 5) was significantly higher in the diuretic group (p less than 0.01). The serum potassium was significantly lower (p less than 0.001) in the diuretic group, and there was a significant (p less than 0.005) inverse correlation between the number of VPBs and the serum potassium in all treated patients. The patients with complex arrhythmias were older (p less than 0.01) than the remainder of the patients. No correlation between serum magnesium and VPBs or complex arrhythmias was found. This study demonstrates increased frequency of VPBs in older hypertensive males, treated with diuretics, and that hypokalaemia predisposes to increased cardiac arrhythmias. We conclude that in older mildly hypertensive men hypokalaemia should be avoided.

Supraventricular tachycardia: diagnosis and management

Supraventricular tachycardia (SVT) includes all forms of tachycardia that either arise above the bifurcation of the bundle of His or that have mechanisms dependent on the bundle of His. We conducted a review of the techniques used to differentiate the mechanisms of SVT. We searched the PubMed and MEDLINE databases for English-language literature published from 1970 to 2008. Articles were selected for either their historical importance or up-to-date clinical data. This review focuses on techniques for scrutinizing electrocardiograms of patients, analyzing in particular the onset of tachycardia, the mode of tachycardia termination, and the effects of premature ventricular contractions, premature atrial contractions, and aberrancy during tachycardia. Both short-term and long-term management of SVT are examined, including the urgent treatment of patients in the emergency department. This review also describes management of patients who have ongoing symptomatic SVT, outlining such available treatment options as atrioventricular node-blocking drugs, antiarrhythmic drugs, and catheter ablation.

Changes in spontaneous variability of ventricular ectopic activity as a function of time in patients with chronic arrhythmias

Previous determinations of spontaneous variability in ventricular arrhythmia have often been based on measurements from consecutive days in small patient populations, whereas clinical determinations of drug efficacy typically compare measurements at intervals of 1 week and longer to baseline. We, therefore, sought to determine whether spontaneous arrhythmia variability changes as a function of time during periods ranging from 1 day to 1 year or longer. The percent reduction in the frequency of total premature ventricular complexes (PVCs) and repetitive ventricular beats required to show true drug effect rather than spontaneous variability in PVCs was determined in 47 consecutive patients with chronic ventricular arrhythmias who underwent multiple ambulatory monitor recordings while off active drug treatment (during placebo therapy). The variability in PVC rate was determined during the intervals of 1 day, 1 week, 2 weeks, 3 weeks, 4 weeks, and 1 year or longer. The percent reductions in total PVCs required to exceed the 95% confidence limits of spontaneous variability at these intervals were 55%, 85%, 86%, 93%, 96%, and 96%, respectively. Corresponding values for repetitive beats were 75%, 95%, 92%, 95%, 94%, and 98%, respectively. The percent increase in total PVCs and repetitive beats required to establish "arrhythmia aggravation" caused by an antiarrhythmic drug with a 95% confidence limit also was calculated for this study population and was 124% and 303%, respectively, at 1-day intervals and 2,269% and 4,091%, respectively, at 1-year (or longer) intervals for the 24-hour monitor recordings. Variability was not substantially affected by underlying heart disease or ejection fraction. PVC rate showed a modest negative correlation with variability (r = 0.3). Thus, variability is substantially greater at 1 week, the usual time for clinical assessment of antiarrhythmic drug efficacy, than at 1 day (p less than 0.01). Suppression of more than 85% of total PVCs and more than 95% of repetitive beats appears to be necessary after 1-2 weeks to be confident of a true drug effect. Even greater variability is observed after 1 month and up to 1 year so that reductions of up to 95% in total PVCs and 98% in repetitive beats may represent spontaneous change.(ABSTRACT TRUNCATED AT 400 WORDS)

Antiarrhythmic efficacy of Ethmozine (moricizine HCl) compared with disopyramide and propranolol

In the investigation of new antiarrhythmic drugs, comparative trials with clinically available antiarrhythmic agents provide a perspective from which to judge the new investigational agent. Two clinical investigations of moricizine HCl, each using a placebo-controlled, double-blind, crossover design, are summarized. In the first study, 18 patients with greater than or equal to 30 ventricular premature complexes (VPCs) per hour (mean 369 +/- 95) were given propranolol (120 mg daily) compared with moricizine HCl (816 +/- 103 mg daily). Propranolol suppressed 38% of VPCs in the study group, moricizine HCl, 81% of VPCs, and the combination of both drugs, 87%. Moricizine HCl was more effective than propranolol in suppressing VPCs at all individual levels greater than 70% (p less than 0.05, McNemar's test). The combination of moricizine HCl and propranolol was well tolerated. The second investigation used a placebo-controlled, double-blind, crossover design to compare the efficacy of disopyramide (600 mg daily) and moricizine HCl (800 mg daily) in 27 patients. Patients had greater than or equal to 40 VPCs/hr on a 24-hour ambulatory electrocardiogram. During moricizine HCl administration, the mean VPC frequency decreased from 524 to 151 VPCs/hr (71.2% reduction). In contrast, disopyramide reduced VPC frequency from 535 to 253 VPCs/hr (52.8% reduction) and demonstrated significantly greater side effects (p less than 0.05). Moricizine HCl was more effective than disopyramide in suppressing VPCs at all individual percent reduction levels greater than 70% (p less than 0.05, McNemar's test). Moricizine HCl was more effective in suppressing VPCs than either disopyramide or propranolol, with significantly fewer side effects.

Spontaneous arrhythmia detected on ambulatory electrocardiographic recording lacks precision in predicting inducibility of ventricular tachycardia during electrophysiologic study

This study investigates the relation of spontaneous ventricular arrhythmia on ambulatory electrocardiographic (ECG) monitoring to the subsequent inducibility of ventricular tachycardia during programmed electrical stimulation. Eighty patients (65 men, 15 women), whose mean age was 58 years, presented with one of the following: sustained ventricular tachycardia (n = 54); sudden death requiring resuscitation (n = 4); ventricular fibrillation (n = 11); or syncope thought to be of cardiac origin (n = 11). All patients had 24 hour ambulatory electrocardiograms and programmed electrical stimulation while receiving no antiarrhythmic therapy. Programmed electrical stimulation resulted in inducible sustained ventricular tachycardia (defined as a rate of greater than or equal to 120 beats/min for greater than or equal to 1 minute or requiring intervention) in 53 of the 80 patients. There was no measure of frequency or complexity of spontaneous arrhythmia detected on ambulatory ECG that could identify the degree of subsequent ventricular tachycardia inducibility during programmed electrical stimulation. In fact, 25% of patients who had inducible sustained ventricular tachycardia had little or no spontaneous arrhythmia on ambulatory ECG. Furthermore, of the 53 patients with inducible sustained ventricular tachycardia, 28 and 55% had no couplets or nonsustained ventricular tachycardia, respectively, during ambulatory monitoring. The combination of a clinical presentation of sustained ventricular tachycardia, confirmed coronary artery disease and a left ventricular ejection fraction of less than 30% had a better positive predictive value than did any ambulatory ECG criterion in predicting the inducibility of sustained ventricular tachycardia.

Spontaneous variability of ventricular arrhythmias in patients at increased risk for sudden death after acute myocardial infarction: consecutive ambulatory electrocardiographic recordings of 88 patients

The Cardiac Arrhythmia Pilot Study, sponsored by the National Heart, Lung, and Blood Institute, is a multicenter, prospective, randomized, double-blind trial designed to identify patients having 10 or more ventricular premature complexes (VPCs) per hour within 6 to 60 days of acute myocardial infarction. The present investigation selected patients after acute myocardial infarction who had ambulatory electrocardiographic qualifying arrhythmia for CAPS. An additional baseline electrocardiogram was recorded before enrollment in the study to assess baseline spontaneous variability of VPCs. A total of 88 patients (15 women, 73 men, aged 57 +/- 10 years) were studied. The 43 patients (49%) receiving beta-blocking drugs were included because the dose was not altered between the 2 consecutive electrocardiographic recordings. This investigation shows that a 95% reduction in VPCs is required to document a significant drug effect rather than variability alone if 1 day of control and 1 day of treatment electrocardiographic recording are compared. Similarly, based on 1 day of electrocardiographic recording before and after antiarrhythmic therapy, 1,780% increase in VPC frequency is required to establish "arrhythmia aggravation" from an antiarrhythmic drug rather than from variability alone based on a 95% confidence interval. Variability of ventricular arrhythmias is independent of left ventricular function, whereas patients taking beta-blocking therapy tend to have greater VPC variability (p = 0.052), even though VPC frequencies were lower (59 +/- 19 vs 138 +/- 31 VPCs/hour, p less than 0.006) than those not taking beta-blocking drugs.

Asymptomatic telephone ECG transmissions as an outpatient surveillance system of ventricular arrhythmias: relationship to quantitative ambulatory ECG recordings

Although ambulatory ECG recordings provide quantitative information in the follow-up of patients with ventricular arrhythmias, they are performed infrequently, potentially missing serious arrhythmias in the unmonitored periods. Telephone ECG systems offer "real-time" ECG information, theoretically functioning as an arrhythmia surveillance system. Thus we incorporated frequent telephone ECG transmissions in two antiarrhythmic drug protocols. The first investigation was designed to show the relationship of telephone and ambulatory ECGs in patients with frequent ventricular tachycardia (VT). The second protocol selected patients with "nonlife-threatening" frequent premature ventricular complexes (PVCs) in whom a second placebo period was instituted to simulate the clinical situation of asymptomatic arrhythmia increase. In both drug trials there was a strong linear relationship between the log-transformed PVC counts of telephone ECG and concomitant PVC, couplet, and VT frequencies on ambulatory ECG. In the VT population, greater than or equal to 1 PVC on telephone ECG reflected the presence of VT on ambulatory ECG (sensitivity 87%; specificity 77%). In the second study, telephone ECG transmissions with PVCs on three consecutive transmissions reflected the change from less than or equal to 10 PVCs/hour to greater than or equal to 40 PVCs/hour on ambulatory ECG within 48 hours. These data support the concept that daily surveillance by means of telephone ECG provides arrhythmia information of qualitative clinical relevance.

The changing base line of complex ventricular arrhythmias. A new consideration in assessing long-term antiarrhythmic drug therapy

Initial base-line electrocardiograms are used to assess the efficacy of treatment for ventricular arrhythmias. This approach assumes that in the absence of treatment the frequency of arrhythmia would remain constant. To test the validity of this assumption, we studied 26 clinically stable patients with symptomatic but not life-threatening ventricular arrhythmias, during two periods of placebo treatment separated by a mean of 17 months. As compared with the initial placebo period, there were significant reductions in ventricular premature depolarizations (50 per cent), pairs (65 per cent), and ventricular tachycardia (83 per cent) during the second period of placebo administration (P less than or equal to 0.05 for all comparisons). Over one third of the patients gave the appearance of receiving successful therapy during the second placebo period, even when the reported spontaneous variability of ventricular arrhythmia was taken into consideration. If unrecognized, these long-term spontaneous changes in the frequency of arrhythmia could result in continuation of unnecessary and potentially toxic therapy and lead to incorrect conclusions regarding the efficacy of antiarrhythmic drugs in clinical trials. We therefore recommend that the frequency of arrhythmia be reassessed annually in the absence of treatment in patients similar to those in our study. These recommendations should not be applied to patients with life-threatening ventricular arrhythmias.

Incidence of complex ventricular arrhythmias in asymptomatic patients with recent myocardial infarction

The incidence of ventricular extrasystoles (VES) was documented in 50 patients with recent uncomplicated myocardial infarction, with a 72-h two-channel ambulatory electrocardiogram. All patients were free of symptoms of arrhythmias; unstable angina pectoris and heart failure were absent. A total of 82% of the patients had VES: 23/50 patients had multiform or complex VES, 8/50 patients had ventricular tachycardia. VES were independent of heart rate and stable angina pectoris. Thus, frequent and complex VES are common in asymptomatic patients with uncomplicated recent myocardial infarction. Even in the absence of symptoms, ambulatory electrocardiography is useful. The prognostic significance of asymptomatic complex VES in these patients remains unsettled.

Analysis of the spontaneous variability of ventricular arrhythmias: consecutive ambulatory electrocardiographic recordings of ventricular tachycardia

Results are reported of analysis of the variability of complex ventricular arrhythmias in a cohort of 110 patients selected for the presence of ventricular tachycardia (VT). All patients were enrolled in investigational antiarrhythmic drug trials and had an average of 4 consecutive days of placebo ambulatory electrocardiographic recording to serve as the database for this study. Using a statistical approach incorporating analysis of variance, the minimum percent reductions of ventricular premature complexes, couplets and VT were calculated to establish "drug effect" rather than variability at a significance level of 0.05. The relative variability of ventricular arrhythmias in prognostically important groups was also analyzed: (1) coronary artery disease (CAD) (n = 57) vs no CAD (n = 53); (2) patients with a left ventricular ejection fraction of 40% or less (n = 52) vs those with an ejection fraction greater than 40% (n = 58); and (3) patients with frequent runs of VT (10 or more runs/day, n = 63) vs infrequent VT (n = 47). Multiple regression analysis revealed that patients with CAD have significantly greater premature ventricular complex variability than patients without CAD (p less than 0.01). Also, patients with frequent VT runs have greater VT variability than that previously reported in smaller studies, thus requiring greater VT reductions to establish drug effect. Whether the variability of ventricular arrhythmia is itself an independent risk factor for sudden cardiac death is unknown.

Comparison of propafenone and disopyramide for treatment of chronic ventricular arrhythmias: placebo-controlled, double-blind, randomized crossover study

In a double blind, placebo-controlled study, the efficacy of propafenone, a new antiarrhythmic drug was compared to that of disopyramide. Sixteen patients with frequent and complex premature ventricular contractions (PVCs) were studied by serial 24-hour ambulatory monitoring, while they were receiving propafenone, 300 mg, and disopyramide, 200 mg, both every 8 hours. A reduction in the mean frequency of PVCs per hour, in comparison to the placebo period, from 574 +/- 535 to 100 +/- 130, was observed after propafenone (p less than 0.005) and from 629 +/- 455 to 231 +/- 280 after disopyramide (p less than 0.008). A greater than 70% reduction in PVCs in comparison to placebo was observed in 11 of 14 after propafenone and 9 of 15 after disopyramide (NS). A greater than or equal to 90% reduction in PVCs was observed in 9 of 16 with propafenone and in 4 of 15 with disopyramide (p less than 0.05). The suppression of complex PVCs (repetitive, polymorphic, or more than 5/min with bigeminism) was observed in 11 of 14 after propafenone and in 9 of 14 after disopyramide. The abolition of nonsustained ventricular tachycardia was observed in 6 of 6 and 3 of 5, respectively, after propafenone and disopyramide (p less than 0.05). A lower incidence of side effects, 4 of 16 vs 8 of 16, was observed during propafenone than during disopyramide treatment. We conclude that propafenone, in a dose of 900 mg daily, is more effective than disopyramide, in a dose of 600 mg daily, in the treatment of frequent and complex PVCs and nonsustained ventricular tachycardias. Propafenone also showed a lower incidence of side effects.

Can cardiac death be predicted from an ambulatory 24-hour ECG?

For the prediction of cardiac death significant prognostic information can be derived from ambulatory 24-hr ECGs when they are recorded on indication in the cardiological outpatient-clinic. In both CHD and non-CHD patients, ventricular arrhythmias, supraventricular arrhythmias and conduction disturbances are all of importance in the assessment of prognosis. These conclusions are based on a review of all 123 cardiac deaths and 433 randomly selected survivors from a cohort of 5095 patients who underwent 24-hr ECG-recording on clinical indication and whose survival status was ascertained 18 months after the recording date.

The role of Holter monitoring in patients with recurrent sustained ventricular tachycardia: an electrophysiologic correlation

The significance of spontaneous ventricular premature depolarization (VPD) frequency and severity in patients with sustained ventricular tachycardia undergoing serial electrophysiologic studies (EPS) are unknown. Nineteen patients with sustained ventricular tachycardia were studied with 24-hour Holter recordings prior to control EPS and prior to each drug trial. Successful drug or surgical treatment (with the exception of amiodarone) was based upon noninducibility of ventricular tachycardia in the laboratory. Among the eight noninducible and nonamiodarone medically treated patients, two (25%) had significant VPD reduction and/or Lown class improvement. The remaining six (75%) had no change or worsening of Holter findings, despite noninducibility of sustained VT. Among the six amiodarone-treated patients, five of whom were persistently inducible prior to discharge, four (66%) had improved and two (33%) had worsened Holter findings compared to control. None of the five (100%) surgically managed patients were inducible postoperatively, and three of the five (60%) had no change or worsening of Holter findings. We conclude that (1) EPS are superior to Holter findings in assessing successful management; and (2) Holter findings may be concordant or discordant during EPS serial drug trials or following surgery and therefore cannot predict the success or failure of the intervention.

Diuretic-induced hypokalemia in uncomplicated systemic hypertension: effect of plasma potassium correction on cardiac arrhythmias

Sixteen patients with diuretic-induced hypokalemia underwent 24-hour ambulatory electrocardiographic monitoring during and after correction of hypokalemia. Plasma potassium averaged 2.83 +/- 0.08 mEq/liter before and 3.73 +/- 0.06 mEq/liter after correction with potassium chloride, triamterene or both. Premature atrial contractions decreased in 6 patients, increased in 6 and remained unchanged in 4. There was no improvement in ventricular ectopic activity after plasma potassium correction. Ventricular ectopic activity improved in 5 patients, worsened in 10 and remained unchanged in 1. Ventricular tachycardia was not observed in either phase. Plasma magnesium remained normal throughout. The investigators conclude that in patients with uncomplicated hypertension, correction of diuretic-induced hypokalemia does not significantly reduce the occurrence of spontaneous atrial or ventricular ectopic activity.

Analysis of ambulatory electrocardiograms in 15 patients during spontaneous ventricular fibrillation with special reference to preceding arrhythmic events

Fifteen patients sustained ventricular fibrillation during ambulatory electrocardiographic recording in a period of 3.5 years over which time 16,500 ambulatory electrocardiograms were analyzed (prevalence = 0.09% or 1/1,100). Eight patients died, and seven survived cardiopulmonary resuscitation. Quantitative analysis of hourly ventricular arrhythmias prior to ventricular fibrillation revealed an increased frequency of premature ventricular beats and ventricular tachycardia, especially in the 2 hours immediately before ventricular fibrillation. Ventricular fibrillation was initiated by ventricular tachycardia in all 15 cases. These runs of ventricular tachycardia were characterized by their unusual length (mean = 560 +/- 536 beats) and their rapid rate (241 +/- 45 beats/min). Although an R on T premature ventricular beat initiated ventricular tachycardia and ventricular fibrillation occasionally, the mean prematurity index of the initiating premature ventricular beat was not early (mean = 1.27 +/- 0.28). QT prolongation was present in only 3 of the 15 patients (mean QTc interval = 0.42 +/- 0.06). Left ventricular dysfunction (mean left ventricular ejection fraction = 34.9 +/- 9.9%) and coronary artery disease were nearly always present. The cardiac medications most frequently associated with these patients at the time of ventricular fibrillation were digitalis and quinidine.

A system for the analysis of long-term electrocardiographic studies in clinical research and training

A computer system has been developed for the analysis of data from long-term electrocardiographic studies in the context of an institution committed to clinical research and training. The major characteristics required of such a system are intelligence, flexibility, friendliness, and maintainability. These attributes are achieved by a user interface which consists of menus and interactive graphics, and by the use of highly modular software developed in a high-level programming language. The system has been used in studies of the effects of drugs on cardiac arrhythmias and has been easy to learn and convenient to use.

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.

Ethmozine suppression of single and repetitive ventricular premature depolarizations during therapy: documentation of efficacy and long-term safety

This study reports a total of 1677 patient days' experience with the use of Ethmozine to suppress ventricular premature depolarizations. A total of 39 patients were studied on three placebo-controlled protocols. Ethmozine, given at a mean total daily dose of 830 mg +/- 318 mg on a dosing schedule of every 8 hours, resulted in a mean plasma Ethmozine level of 0.42 micrograms/ml +/- 0.28 micrograms/ml. In addition to reducing ventricular premature depolarizations from 11,049/24 hr during placebo to 2231/24 hr during Ethmozine therapy (80% reduction), the drug also resulted in a 95% reduction in paired forms and a 99% reduction in total runs of ventricular tachycardia. Ethmozine is extraordinarily well tolerated with only mild side effects of dizziness, perioral tingling, and euphoria, with no serious toxicity requiring discontinuation of therapy. Ethmozine demonstrates great potential as an effective drug in suppressing ventricular premature depolarizations with minimal side effects or toxicity.

Chronic tocainide therapy for refractory high-grade ventricular arrhythmias

Tocainide, an oral analog of lidocaine, was evaluated as a long-term antiarrhythmic agent in 21 patients with symptomatic complex ventricular ectopic activity (10 with hemodynamically significant ventricular tachycardia) refractory to currently available antiarrhythmics singly, and in combination for periods of 3 days to 35 months (mean 13.6 months). Tocainide appeared to be an effective and safe agent for the control of these refractory symptomatic ventricular arrhythmias in 14 of the 21 patients (66%). Minor central nervous system and gastrointestinal side effects were present in most of the patients, usually early on in therapy, and only precluded long-term use in 2 patients. Furthermore, lidocaine responsiveness was a good predictor of tocainide effectiveness in this group of patients. Tocainide precipitated atrioventricular (A-V) block in one patient with pre-existing A-V nodal disease; two patients developed a skin rash while on tocainide therapy. These two patients had previously developed lupus-like syndromes and skin rashes while on procainamide. The ANA titers had been falling in these two patients while on tocainide, and in one of these patients with true systemic lupus erythematosus, rechallenge with tocainide failed to produce skin rash. Tocainide's long plasma half-life and high oral bioavailability permit an 8-h regime. We conclude that tocainide is an effective, safe antiarrhythmic agent with tolerable side effects.

Prajmalium bitartrate in chronic ventricular arrhythmias: comparison with disopyramide

24-h ECG recordings were used to assess the efficacy of prajmalium bitartrate (PB) in reducing the incidence and the severity of premature ventricular complexes (PVCs), and to compare its antiarrhythmic action with that of Disopyramide. 13 patients with frequent PVCs were distributed randomly into 2 groups. The first group of 7 patients received PB 80 mg/day for 4 days as their first treatment, and disopyramide 400 mg/day for a further 4 days as the second therapy. The succession of the drugs was reversed in the other group of 6 patients. Analysis of the Holter recordings showed that PB and disopyramide reduced PVC frequency to a similar extent as compared to the corresponding wash-out period, viz. by 56.7% (p less than 0.05) and 62.1% (p less than 0.01), respectively. Thus, PB appears to be an effective antiarrhythmic drug and comparable to disopyramide. It may be used to prevent premature ventricular complexes and runs of ventricular tachycardia.

Malignant ventricular arrhythmias in chronic chagasic myocarditis

We studied 28 cases of chronic chagasic myocarditis (CCM) with frequent ventricular arrhythmias. Two-hundred and three conventional ECGs recorded during 3 months showed ventricular extrasystoles (VE) ranging between 0.2 and 6 per ten beats in 100%; multiform VE in 97.04%; couplets in 79.31%; ventricular tachycardia (VT) in 42.85%; and R on T in 21.67%. A 24-hour continuous recording showed that VE ranged between 3780 and 61733 (mean 16618 +/- 2627); multiform VE and couplets were present in 100% of patients, and VT was present in 78.5%. In 16 patients (group I) the frequency of VE was persistently high, without diurnal variation; 11 patients showed sustained reduction during sleeping hours and only one showed an increase during night sleep (group II). Even in group II, VE never disappeared for periods longer than 10 minutes. In five patients, four 24-hour recordings were obtained at weekly intervals, and in five other patients a second 24-hour recording was performed 10 to 24 months later. The remarkable frequency, persistence and low variability of ventricular arrhythmias in CCM suggest that such arrhythmias can be used as a most stable, reliable, but highly demanding model for testing the efficacy of antiarrhythmic drugs.

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 prospectively assessed in 99 patients with hypertrophic cardiomyopathy. In the absence of antiarrhythmic 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 less than 0.02). In summary, (1) high grade ventricular arrhythmias are commonly found on continuous 24 hour electrocardiography 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 electrocardiography 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 antiarrhythmic therapy if ventricular tachycardia is identified.

Diuretic-induced ventricular ectopic activity

The need to avoid hypokalemia during diuretic therapy in nondigitalized patients has been questioned. Twenty-one patients with (1) mild essential hypertension, (2) plasma potassium of less than 3.5 meq/liter during previous diuretic treatment, and (3) normal findings [less than 6 unifocal ventricular premature beats/hour] on 24-hour ambulatory electrocardiographic monitoring and exercise testing were treated with hydrochlorothiazide (50 mg twice a day) for four weeks and then ambulatory electrocardiographic monitoring and exercise testing were repeated. Ambulatory electrocardiographic monitoring revealed that ventricular ectopic activity developed in seven patients and complex ventricular ectopic activity (multifocal ventricular premature beats, ventricular couplets and/or ventricular tachycardia) in four. Only two of these seven had ventricular ectopic activity during exercise testing while they were hypokalemic. Potassium repletion in these seven patients with spironolactone abolished complex ventricular ectopic activity and reduced unifocal ventricular premature beats significantly (p less than 0.01) from an average of 71.2 ventricular premature beats/hour/patient during hydrochlorothiazide treatment to 5.4 ventricular premature beats/hour/patient after potassium repletion. Although complex ventricular ectopic activity was more likely to occur with plasma potassium less than 3.0 meq/liter, restoration of normokalemia was required in several patients to abolish residual ventricular ectopic activity. Persistent ventricular ectopic activity in one patient suggested that myocardial injury sustained during hypokalemia may initiate chronic ventricular ectopic activity. Even in nondigitalized patients, the hazard of diuretic-induced ventricular ectopic activity warrants correction of hypokalemia.

Spontaneous variability of complex ventricular arrhythmias detected by long-term electrocardiographic recording

Variations in the frequency of complex ventricular arrhythmias were evaluated by consecutive 24-hour long-term electrocardiographic recordings over 4 days using a two-channel recorder and computer-assisted analysis system with a weighted relative mean error of 7.5 +/ 5% (SD). Twenty patients (mean age 58 +/- 9 years [SD] with various cardiac disorders were selected if they had a daily average of more than 30 ventricular ectopic complexes per hour. Twenty patients had ventricular couplets and 14 patients had ventricular tachycardia (at least triplets). The mean daily number of either couplets or ventricular tachycardia was subjected a four-factor nested analysis of variance to determine the sources of variation in ectopic frequency. Differences in hourly rates accounted for 30% of the variation in the frequency of ectopic complexes. Statistical methods were applied to determine the change in frequency of complex arrhythmias necessary to exceed that attributable to spontaneous variation alone at the p less than 0.05 level. Using a typical protocol, for example, comparing a 24-hour test period with a 24-hour control period would require a 65% decrease in mean hourly frequency of ventricular tachycardia and 75% reduction in the frequency of couplets to demonstrate therapeutic efficacy rather than a reduction due to spontaneous variation alone.

Research related to noninvasive instrumentation

In the past three decades, techniques that permit noninvasive quantitation of the function of the heart have been developed. Exercise electrocardiography has been widely used to determine the presence or absence of ischemic heart disease. Echocardiography permits detection of valvular, congenital and arteriosclerotic disease and quantitation of its severity. Selective use of isotopes allows nuclear angiogarphy, myocardial perfusion studies and detection of damage to cellular myocardium. New techniques such as computerized axial tomography, magnetometry, focused pulsed Doppler, and wider application of computer-enhanced image processing are important future directions for noninvasive monitoring.

Evaluation of aortocoronary venous bypass grafting for prevention of cardiac arrhythmias

The influence of ACB on cardiac arrhythmias was examined in 27 patients. Eight-hour Holter monitoring was performed 8 days preoperatively and 100 days postoperatively. Arrhythmias were divided into 3 groups (Class I: NSR +/- occasional APBs; Class II: less than five unifocal VPBs per minute; Class II: more than five VPBs per minute, multifocal VPBs, VPBs in a row or VT). Preoperative classification disclosed that 13 patients (48.1 per cent) were in Class I, six patients (22.2 per cent) were in Class II, and eight patients (29.6 per cent) were in Class III. The corresponding values after surgery were 10 patients (37.0 per cent), 13 patients (48.1 per cent), and four patients (14.8 per cent). These differences were not statistically significant (p less than 0.1). In view of the tendency of arrhythmias of Class III to improve after ACB, we feel that further investigations in this area are needed. At the present time ventricular arrhythmias alone constitute no indication for bypass surgery.

Antiarrhythmic drug therapy in survivors of prehospital cardiac arrest: comparison of effects on chronic ventricular arrhythmias and recurrent cardiac arrest

We studied the long-term effects of membrane-active antiarrhythmic agents on chronic ventricular arrhythmias in patients who have survived prehospital cardiac arrest. Among 16 patients treated with a dose-adjusted, plasma level-monitored antiarrhythmic regimen, eight have survived for longer than 12 months and eight have had recurrent cardiac arrests (RCAs). Monthly Holter monitor tapes (HM) recorded during the 4 months before the eight RCAs were compared with monthly HM tapes matched for time of entry and duration of follow-up in the eight patients who did not have RCAs. Transient or persistent complex ventricular ectopic depolarizations (VEDs) have been recorded on 47 of the 63 monthly HM tapes (75%). The difference between VEDs in the RCA patients (mean 153 VEDs/hr, median 19 VEDs/hr) and VEDs in the patients who have not had RCA (mean 122 VEDs/hr, median 8 VEDs/hr) was not significant (p less than 0.2); nor was there a predictable relationship between therapeutic plasma levels of antiarrhythmic agents and the frequency and complexity of chronic asymptomatic VEDs (therapeutic levels--mean 104 VEDs/hr, median 6 VEDs/hr; subtherapeutic levels--mean 184 VEDs/hr, median 21 VEDs/hr). Differences were not significant (p greater than 0.1). In contrast, all eight RCA patients had unstable plasma levels (21 of 31 determinations subtherapeutic) while six of the eight patients who have not had RCA had consistently therapeutic levels (p less than 0.01). Thus, adequate plasma levels of antiarrhythmic agents may protect against RCA, despite failure to suppress VEDs predictably. The apparent dissociation between predictable suppression of chronic VEDs and protection against RCA suggests that clinical effectiveness of these agents may not be best measured by their effect on chronic VEDs.