Question

1. Steven had a left ventricular wall infarction secondary to myocardial ischemia. This damage to the left ventricle compromised its function as a pump; the left ventricle could no longer generate enough pressure to eject blood normally. Draw the normal Frank–Starling relationship for the left ventricle. Superimpose a second curve showing the Frank–Starling relationship after the myocardial infarction, and use this relationship to predict changes in stroke volume and cardiac output.

7. What was the rationale for treating Steve with furosemide (a loop diuretic)?

8. A medical student in the coronary intensive care unit asked whether Steven should also be treated with propranolol (a β-adrenergic antagonist). The student reasoned that propranolol would reduce the myocardial O₂requirement and possibly prevent another infarction. Why does propranolol decrease the myocardial O₂requirement? The attending physician pointed out that there could be a risk associated with the use of propranolol. What is this risk?

9. Why was Steven sent home on a low-Na⁺diet?

Answer 1

1)Frank Starlin mechanism is an cardiac auto regulatory mechanism of stroke volume and end diastolic volume. In Frank starling curve we draw stroke volume on the Y axis and pre-load (left ventricular end diastolic pressure )on the X axis. And make relationship between stroke volume and pre-load.

The Frank starling curve is

The normal heart have increase pre-load will result in increased stroke volume. In abnormal cases

Left shift:higher stroke volume and increased contractility due to exercise or ionotrops and decrease peripheral vascular resistance (after load)

Right shift :decrease contractility die to myocardial infarction and increase peripheral vascular resistance (after load) due to vasopressor..

In left ventricular failure the weakened ventricular muscle are unable to pump enough blood to aorta and it will result in decreased contractility and stroke volume and decreased stroke volume will result in decreased cardiac output .

7)furosemide is a loop diuretics and it help to decrease fluid over load. In the case of Steve the left ventricular heart failure happened ,if we administered loop diuretics in this case it will help to eliminate sodium and fluid via the kidney therefore it will decrease the workload of heart and it also helpful to treat pulmonary congestion result from heart failure.

8)The propranalol is a beta blocker drug that is used in several condition like MI, migraine ,anxiety etc. In myocardial infarction the propranalol block the action of catecholamin by blocking the both beta1 and beta 2 adrenergic receptors and inhibiting the sympathetic effect and it will result in decreased cardiac muscle function and decrease oxygen requirement. But this drug is contraindicated in congestive cardiac failure because it will result in decrease stroke volume and cardiac output and it have negative ionotropic effect leads to decrease blood pressure.

9)sodium is an essential elements that help to keep our fluid levels with in normal limit. The low sodium diet is good for patient with cardiac diseases because high sodium intake leads to increase fluid volume and increase blood pressure it will result in increased work load of heart and later heart failure occurred and high sodium accelerate the post infarction ventricular remodeling. So low sodium diet is necessary for Steve to maintain health status of heart.