Key Points
- To determine whether beta-adrenergic stimulation with isoproterenol can improve left ventricular relaxation and filling in hypertrophic cardiomyopathy compared with atrial pacing tachycardia.
- Evaluated 12 patients with hypertrophic cardiomyopathy during atrial pacing stress and during isoproterenol infusion matched to comparable heart rates.
- Measured simultaneous left ventricular pressure using micromanometer catheters, volume and regional systolic asynchrony via radionuclide angiography, and myocardial lactate metabolism.
- Isoproterenol provoked myocardial ischemia with reduced lactate consumption in 9 of 12 patients, while producing higher peak left ventricular pressure (205 ± 33 vs. 142 ± 21 mm Hg, p < 0.001) and higher ejection fraction (77 ± 10% vs. 71 ± 12%, p < 0.02) compared to pacing.
- Despite ischemia, isoproterenol enhanced diastolic function by reducing the pressure decline half-time T 1/2 (46 ± 10 to 33 ± 6 msec, p < 0.001) and increasing end-diastolic volume (77 ± 18% to 100 ± 11% of control, p < 0.001) with unchanged end-diastolic pressure (19 ± 7 to 19 ± 5 mm Hg, p = NS).
Structured PICO
Does isoproterenol improve left ventricular diastolic performance compared to rapid atrial pacing in patients with hypertrophic cardiomyopathy?
PPopulation12 patients with hypertrophic cardiomyopathy
IInterventionIsoproterenol infusion to similar heart rates as pacing
CComparatorRapid atrial pacing stress to induce myocardial ischemia
OOutcomeLeft ventricular diastolic performance (including T 1/2 of pressure decline, pressure-volume relations, and end-diastolic volume) and lactate metabolismsurrogate
In patients with hypertrophic cardiomyopathy, beta-adrenergic stimulation with isoproterenol improves left ventricular relaxation and filling compared to tachycardia alone, despite exacerbating myocardial ischemia.