ABNORMAL CORONARY FLOW DYNAMICS AT REST AND DURING TACHYCARDIA ASSOCIATED WITH IMPAIRED LEFT-VENTRICULAR RELAXATION IN HUMANS - IMPLICATIONFOR TACHYCARDIA-INDUCED MYOCARDIAL-ISCHEMIA

Objectives. This study attempted to clarify the effect of ventricular relaxation abnormalities on coronary dow dynamics at rest and during t achycardia in humans. Background. Ventricular relaxation abnormality h as been demonstrated in animals to have an adverse impact on early dia stolic coronary flow dynamics. However, this relation has not been est ablished in humans. Even if the adverse effect were latent at rest, it might become evident during tachycardia because tachycardia reduces c oronary flow reserve and facilitates the production of myocardial isch emia. Methods. Doppler phasic left coronary flow velocity pattern was obtained at rest and during tachycardia in 23 patients without coronar y stenosis. The time constant of left ventricular isovolumic pressure (tau) was used to assess ventricular relaxation. Results. The time to peak flow velocity of the diastolic coronary flow wave was longer, and the fraction of the first third of diastolic coronary how was smaller , in patients with a longer tau (r = 0.58, p < 0.01; r = -0.44, p < 0. 05), indicating a close relation between early diastolic coronary flaw dynamics and ventricular relaxation. Although rapid atrial pacing yie lded an increase in the coronary how velocity integral per minute in a ll patients, diastolic coronary how velocity integral per minute incre ased in 9 patients with a normal (less than or equal to 40 ms) tau at rest but decreased in 14 patients with a longer (>40 ms) tau at rest. Conclusions. Impaired left ventricular relaxation was associated with decreased coronary flow in early diastole at rest and decreased corona ry flow throughout diastole during tachycardia in patients without cor onary stenosis. These findings may provide more insight into the mecha nism of tachycardia-induced subendocardial docardial ischemia in patie nts with impaired ventricular relaxation but without concomitant coron ary stenosis.