01 Nov

New Exercise Parameter for the Identification of Severe Coronary Artery Disease: Outcome

Crawford et al demonstrated that an abnormal SBP-RR (defined as a SBP-RR >1.0, >0.9, >0.8 at respectively 1, 2, and 3 minutes in the recovery period) is equal in sensitivity to exercise thallium 201 scintigraphy in detecting single vessel disease. Finally, Mohan and Wasir observed that after coronary artery bypass surgery, the SBP-RR returned back toward normal. The diagnostic utility of this new exercise parameter is particularly important in view of the known limitations in interpretation of ST segment changes along with reduced functional capacity in patients receiving antianginal drugs such as beta blockers. Reading here

The exact mechanism of progressive increase in the recovery period systolic blood pressure is unknown; however, the available data suggest that in the postexercise period when ischemia is relieved and left ventricular function returns toward normal, there may be augmentation of contractility possibly under the influence of elevated catecholamines. This course of events has been suggested by Pfisterer et al who observed that in patients with documented coronary artery disease undergoing supine bicycle exercise, the LV ejection fraction progressively increases in the recovery period predominantly in patients demonstrating a decline in the exercise ejection fraction. Similarly, Crawford et al observed that abnormal SBP-RR is associated with an abnormally elevated stroke volume measured with exercise echocardiography during the recovery period. We have prospectively observed that the SBP-RR is related to exercise hemodynamic parameters. The peak systolic blood pressure and heart rate were 196 mm Hg and 132 beats per minute in the normal group compared to 146 mm Hg and 119 beats per minute in patients with an f SBP-RR, respectively. Thus, the underlying mechanism of an f SBP-RR may be related to excessive catecholamine response occurring as a result of exercise induced ischemia and related left ventricular dysfunction. Recently, it has been shown that exercise induced increase in catecholamine levels is greater in patients with three-vessel disease than in those with one- or two-vessel coronary disease. This excessive catecholamine response could result in improvement in left ventricular contractility after relief of ischemia. Horn et al demonstrated augmentation of left ventricular contraction induced by a constant infusion of epinephrine in 16 patients with coronary artery disease. In 11 of these 16 patients, improved contraction in previously asynergic areas was observed. Thus, an improvement in contractility resulting in a greater stroke volume could be responsible for the abnormally elevated systolic blood pressures in the recovery period.

Categories: Coronary Artery
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