Force-frequency relation in patients with left ventricular hypertrophy and failure.

Our study demonstrated a loss of normal systolic contractile enhancement with increasing heart rate in patients with ventricular hypertrophy and symptoms of congestive heart failure. This decline in systolic reserve was not accompanied by worsening of diastolic function, and would therefore not seem to reflect underlying ischemia. Rather, it was more likely related to abnormalities of excitation-contraction coupling, particularly in light of findings of both increased post-rest potentiation and a reduced recirculation fraction. In contrast, mechanical restitution was unchanged, suggesting that alterations in Ca2+ release from the SR did not play a major role. Finally, we showed that increasing heart rate adversely affects the efficiency of ventriculo-vascular coupling in LVH hearts. This suggested another explanation of how dysfunction of cardiac force-frequency behavior can lead to limited cardiovascular reserve and contribute to clinical symptoms of exertional intolerance. Future efforts aimed at enhancing the force-frequency response, perhaps by enhancing the SR-ATPase, or manipulating its regulation, should prove helpful in ameliorating the limitations of LVH patients associated with rapid heart rate.