Left ventricular hypertrophy in response to pressure overload is therefore a natural compensatory mechanism to reduce systolic wall tension. Systolic wall tension, like contractility and heart rate, cannot be estimated numerically. However, the importance lies in understanding the contributing factors and their directional change on myocardial oxygen consumption. The concept of supply and demand is limited in that one cannot quantify the factors influencing oxygen consumption or the blood flow. The strength of the approach lies in recognition of the factors contributing to delivery and consumption of oxygen by myocardium. When inequity between supply and demand occurs, one can attempt directional changes in the above parameters to offset this imbalance (Fig 2). Since the mentioned parameters influencing supply and demand have variable influences, depending upon the location in the myocardium, it is important to identify the area most at risk for ischemia, and then direct attention to changing parameters in a way to improve blood flow to this region. The subendocardium is the first and most susceptible region to ischemia. birth control pills
Figure 2. Factors influencing myocardial oxygen supply and demand.