Hypertrophic cardiomyopathy in pediatric patients: Effect of verapamil on regional and global left ventricular diastolic function

OBJECTIVE: To assess the effects of treatment with verapamil on regional an d global left ventricular (LV) diastolic function in paediatric patients wi th hypertrophic cardiomyopathy (HCM). DESIGN: Twelve patients (age range 5.1 to 12.3 years, median 8.6) with HCM were evaluated during ongoing chronic oral treatment with verapamil (4 mg/k g/day) and four days after withdrawal of therapy. Twelve age- and body surf ace area-matched normal children sen ed as controls. In an echocardiographi c study, global LV diastolic function was evaluated by assessing isovolumic relaxation time (IVRT) and mitral flow indexes, including peak filling rat e normalized to mitral stroke volume (PFR/SV). In addition, regional LV dia stolic function was assessed by pulsed-wave Doppler tissue imaging at the s ubendocardial portion of the middle region of the anterior and posterior in terventricular septum, and anterolateral and inferior walls to measure the peak velocities and the velocity-time integrals of myocardial excursion in both early diastole and atrial systole. In addition, as an index of diastol ic asynchrony (AsyI), the variation in time to peak filling rate, measured as the time from the peak of the Ei wave on the electrocardiogram to the pe ak of the regional E wave, among the four myocardial regions was defined by subtracting the smallest value from the greatest and expressing the differ ence as a percentage of the smallest value. RESULTS: Compared with the controls, patients with HCM without therapy show ed a longer IVRT (P<0.01) and a decrease in PFR/SV (P<0.01) without a compe nsatory increase in filling during atrial systole. Oral administration of v erapamil induced a significant shortening of the IVRT (P=0.003) and an incr ease in PFR/SV (P=0.02). Furthermore, patients with HCM without therapy sho wed a significantly longer time to peak filling rate (P<0.01) associated wi th a decreased peak velocity in early diastole without a concomitant increa se in peak velocity during atrial systole in each of the myocardial regions . Furthermore, the AsyI was higher in the HCM group than in controls (19% v ersus 6%, respectively), and this index was inversely correlated with the P FR/SV ( r=-0.86, P<0.001). The regional diastolic velocity of the myocardiu m at each of the four analyzed regions was not significantly different with verapamil, but the AsyI was significantly lower (P<0.05). CONCLUSIONS: Children with HCM show abnormalities of both global and region al LV diastolic function. In these patients, chronic administration of vera pamil plays a crucial role in the improvement in global LV filling and, as a consequence, in clinical manifestations. The beneficial effects of verapa mil seem to be related to a reduction in diastolic asyncrony more than to s ignificant changes in diastolic velocities of the myocardial fibres.