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  • Title: Effects of transient increase in intrathoracic pressure on hemodynamic determinants of myocardial oxygen supply and demand.
    Author: Pepine CJ, Nichols WW.
    Journal: Clin Cardiol; 1988 Dec; 11(12):831-7. PubMed ID: 3233813.
    Abstract:
    Effects of transient increases in intrathoracic pressure on hemodynamic indexes of myocardial oxygen supply and demand were evaluated in 21 patients with ischemic heart disease. Left ventricular, ascending aortic, and right atrial pressures and electrocardiogram (ECG) were recorded while a Valsalva maneuver was performed during ischemia. Myocardial oxygen demand was assessed from the tension time index (TTI) and cardiac size and potential myocardial oxygen supply were assessed from a diastolic pressure time index (DPTI) and relative changes in supply/demand ratio from DPTI/TTI. During an asymptomatic interval an abrupt but small transient decrease in TTI and cardiac size occurred during phase II (p less than 0.05) of the Valsalva maneuver. DPTI did not change significantly and DPTI/TTI increased (p less than 0.05). When Valsalva maneuver was initiated during angina, 16 patients reported prompt and complete relief of angina, and left ventricular end-diastolic pressure declined following the maneuver. Relief of ischemia occurred uniformly during the latter part of straining (phase II) coincident with the peak reduction in TTI, cardiac size, and increase in DPTI/TTI. These data indicate that a transient increase in intrathoracic pressure results in a decrease in hemodynamic determinants of myocardial oxygen demand and an increase in the myocardial oxygen supply:demand ratio.
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