Changes of left ventricular diastolic function in exercising dogs without and with ischemia.

Abstract

Left ventricular (LV) diastolic function in the absence and presence of regional ischemia was examined in eight conscious dogs chronically instrumented with ultrasonic devices for measuring LV wall thickness and volume. During treadmill exercise, ischemia was induced (hydraulic occluder) to produce less than 10% systolic wall thickening in the ischemic zone. LV filling was assessed by the peak filling rate (PFR), mean filling rates in the first and second halves of filling (mFR, and mFR2), an early filling index from mitral valve opening to minimal diastolic pressure (PDm), and the percentage of atrial filling. Also, LV relaxation (X-) and wall thinning rates during isovolumetric relaxation and the first and second halves of the filling phase were assessed. During control exercise without ischemia, PDm decreased by 2.61 mm Hg (p<0.05) to -1.1 mm Hg and there was a downward shift of the entire LV diastolic pressurevolume (P-V) curve. The LV relaxation rate, PFR, mFR,, and mFR2 were enhanced. Early filling was increased by 116%, the percentage of atrial filling by 118%, and overall diastolic filling by 23% despite a 63% decrease in the filling period. During ischemic exercise, systolic function was depressed compared with the resting state, PDm increased by 4.84 mm Hg (p<0.005) associated with a pronounced rightward and upward shift of the early portion of the P-V curve. LV relaxation rate, PFR, and mFR1 were reduced, the early filling index fell sharply by 62% but percentage of atrial filling was unchanged, while overall diastolic filling decreased by 30%. The thlinning rate of the control wall was enhanced, whereas that of ischemic wall was depressed. Multiple factors contributed to the markedly impaired early and overall diastolic LV filling during ischemia, including impaired systolic function, reduced relaxation rate, nonuniformity of wall motion, an upward shift of the early diastolic P-V curve, and absence of a compensatory increase in late diastolic filling. (Circulation 1990;81:1058- Supported by a National Institutes of Health, Ischemic Heart Disease SCOR research grant HL-17682 from the National Heart, Lung, and Blood Institute and by an endowed chair granted to J.R. by the San Diego County Chapter of the American Heart Association.Address for correspondence: John Ross Jr., MD, Department of Medicine, M-013B, University of California at San Diego, La Jolla, CA 92093.Received April 27, 1989; revision accepted November 6, 1989.human subjects. The stress of rapid pacing has been examined in the presence of clinical coronary heart disease and experimental ischemia, and effects on early filling accompanied by an upward shift of the diastolic pressure-volume (P-V) curve after pacing have been described.

Effect of dynamic exercise on left atrial function in conscious dogs.

“…The observed changes in LV systolic and diastolic function, manifested by augmented LV ejection parameters and a decrease in the time constant of LV myocardial relaxation, are consistent with two recent studies using conscious dogs exposed to treadmill exercise (Miyazaki, Guth, Miura, Indolfi, Schulz & Ross, 1990;Cheng, Igarashi & Little, 1992). In our study the LV end-diastolic dimension did not change and the end-systolic dimension decreased during exercise.…”

Synergistic Adaptations to Exercise in the Systemic and Coronary Circulations That Underlie the Warm-Up Angina Phenomenon

“…In the present study, although the exercise levels were similar, the magnitude of the BEW was 21% greater on second exertion, which points to an improved myocardial relaxation in early diastole. Because ischemia has been shown to slow diastolic relaxation, 42 the higher BEW is consistent with reduced ischemia and, consequentially, improved coronary blood flow. 43 This important increase in the BEW, together with the beneficial energetics afforded by a reduction in ejection time and LV afterload, suggests that enhanced vascular-ventricular coupling, as well as persistent coronary vasodilation and improved cardiac-coronary interaction, play an important role in the improved performance seen on second exertion.…”

Heart rate and force-frequency effects on diastolic function of the left ventricle in exercising dogs.

“…11,16,24 This method has been shown by others to be useful for demonstrating changes in early relaxation between interventions in the same animal.8 Tau also was calculated using a nonzero asymptote25 Use of this approach produced little change in the calculated values for tau (24±4.2 milliseconds at rest, 19.2±5.0 milliseconds during exercise after UL-FS 49, and 14.7±3.5 milliseconds during pacing, all differences significant, P<.01). Fig 1) E-5v1s -, ,-5VI3 * and the largest common maximum volume (50 mL on the paced heart rate curve, corresponding to end diastole, Fig 1).…”

“…Although wide respiratory fluctuations of the intrathoracic pressure are observed during exercise, as shown in a previous study from this laboratory, changes in mean intrathoracic pressure during exercise are very small and the beat-averaging method using intracavitary pressure successfully eliminates effects of changes in intrathoracic pressure. 11 A possible direct effect of the specific bradycardiac drug UL-FS 49 on diastolic events cannot be excluded. However, the action of the drug to selectively suppress the sinus node rate, and other data demonstrating no direct effect on myocardial contractility and systolic events, [16][17][18][19] suggest that UL-FS 49 may not have important direct effects on diastolic properties.…”