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Variability of ventricular arrhythmias in hypertrophic cardiomyopathy and implications for treatment
Insights
Detecting ventricular tachycardia (VT) in hypertrophic cardiomyopathy (HC) requires 72-hour ECG monitoring. Longer monitoring is needed to rule out VT initially, but its prognostic value after 72 hours is unclear.
Area of Science:
- Cardiology
- Electrophysiology
Background:
- Asymptomatic ventricular arrhythmias are common in hypertrophic cardiomyopathy (HC) patients.
- These arrhythmias are linked to sudden cardiac death.
Purpose of the Study:
- To assess the variability of ventricular extrasystoles.
- To determine the optimal duration of electrocardiographic (ECG) monitoring for excluding ventricular tachycardia (VT) in HC patients.
Main Methods:
- 16 HC patients with VT detected within 48 hours underwent 48-168 hours of ECG monitoring.
- Ventricular extrasystole variability and circadian rhythms were analyzed.
- The likelihood of excluding VT based on monitoring duration was calculated.
Main Results:
- VT incidence was 52% during monitoring (median 72 hours).
- Failure to detect VT probabilities: 48% (24h), 23% (48h), 11% (72h).
- A 61% reduction in extrasystoles needed to show intervention effect; circadian rhythm observed.
Conclusions:
- 48-72 hour ECG monitoring is pragmatic for assessing drug intervention in HC patients with detected VT.
- Longer monitoring (5-6 days) is needed to exclude VT initially.
- Prognostic significance of VT detected after 72 hours remains uncertain.
Abstract:
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)