The Systolic to Diastolic Duration Ratio in Children with Heart Failure Secondary to Restrictive Cardiomyopathy

Systole (S) and diastole (D) are fundamental to cardiac function, yet their durations are not routinely evaluated. We defined the S/D duration ratio in 11 children with restrictive cardiomyopathy (CM) and 31 control subjects, using tricuspid regurgitant flow duration. We correlated S/D ratio, S duration, and D duration with heart rate and compared groups. Heart rates of control subjects and patients with restrictive CM were similar (P = .995). The S/D ratio was higher in patients with restrictive CM than in control subjects (1.6 ± 0.81 vs 0.8 ± 0.19, P < .001) as a result of shortened D (0.43 ± 0.13 vs 0.56 ± 0.06, P < .01) and prolonged S (0.58 ± 0.12 vs 0.44 ± 0.06, P < .01). The S/D ratio was highly correlated to heart rate in restrictive CM (r = 0.95, P < .0001). The high S/D ratio found in restrictive CM, found also in dilated CM, suggests that this index is generic to heart failure rather than to a specific disease. The S/D ratio is easily measured using Doppler flow, enhancing echocardiographic assessment of D function in children.