Ventricular filling

Diastole is the period in the cardiac cycle in which relaxation of the myocardium and ventricular filling take place. In an individual with a resting... 

As plasma volume decreases, less blood is available for ventricular filling. 

Hypertension (blood pressure >140/90 mmHg) may be caused by an elevation in cardiac output or excessive vasoconstriction. Diuretics are used in these patients to reduce cardiac output. Assume that the hearts of these individuals are operating on the ascending portion of the cardiac function curve. As the plasma volume is reduced in response to treatment with diuretic drugs, venous return and preload are reduced, as are ventricular filling and stroke volume, and cardiac output, thus bringing blood pressure back within the normal range. 

The benefits result from blockade of //j receptors in the myocardium, which reduces heart rate, myocardial contractility, and BP, thereby decreasing myocardial oxygen demand. The reduced heart rate increases diastolic time, thus improving ventricular filling and coronary artery perfusion. 

Heart failure (HF) is a clinical syndrome caused by the inability of the heart to pump sufficient blood to meet the metabolic needs of the body. HF can result from any disorder that reduces ventricular filling (diastolic dysfunction) and/or myocardial contractility (systolic dysfunction). 

Causes of diastolic dysfunction (restriction in ventricular filling) are increased ventricular stiffness, ventricular hypertrophy, infiltrative myocardial diseases, myocardial ischemia and infarction, mitral or tricuspid valve stenosis, and pericardial disease (e.g., pericarditis, pericardial tamponade). 

Dopamine should generally be avoided in decompensated HF, but its pharmacologic actions may be preferable to dobutamine or milrinone in patients with marked systemic hypotension or cardiogenic shock in the face of elevated ventricular filling pressures, where dopamine in doses greater than 5 mcg/kg/min may be necessary to raise central aortic pressure. 

D End of IVR. The LV pressure falls below CVP and the mitral valve opens. Ventricular filling. 

The y descent The fall at y is caused by passive ventricular filling after opening of the tricuspid valve. 

Thus, the nitrates enable myocardial flow resistance to be reduced even in the presence of coronary sclerosis with angina pectoris. In angina due to coronary spasm, arterial dilation overcomes the vasospasm and restores myocardial perfusion to normal. O2 demand falls because of the ensuing decrease in the two variables that determine systolic wall tension (afterload) ventricular filling volume and aortic blood pressure. 

It is characterized by severe, persisting pain, shock and hypotension with possible development of arrhythmias and is due to severe depression of systolic cardiac performance, systolic arterial pressure is below 80 mm Hg, low cardiac index, ventricular filling pressure is elevated and pulmonary edema may or may not be evident. The most frequent cause is infarction involving more than fourty percent of the left ventricular myocardiam, leading to a severe reduction in left ventricular contractility contradictively and failure of the left ventricular pump. 

Dobutamine causes an increase in cardiac output, a decrease in peripheral vascular resistance, and a decrease in left ventricular filling pressure. 

Measurements of arterial pressure, cardiac output, stroke work index, and pulmonary capillary wedge pressure are particularly useful in patients with acute myocardial infarction and acute heart failure. Such patients can be usefully characterized on the basis of three hemodynamic measurements arterial pressure, left ventricular filling pressure, and cardiac index. One such classification and therapies that have proved most effective are set forth in Table 13-4. When filling pressure is greater than 15 mm Hg and stroke work index is less than 20 g-m/m2, the mortality rate is high. Intermediate levels of these two variables imply a much better prognosis. 

Subset Systolic Arterial Pressure (mm Hg) Left Ventricular Filling Pressure (mm Hg) Cardiac Index (L/min/m2) Therapy... 

RVFP and LVFP = right and left ventricular filling pressures. 

The numerical values are intended to serve as general guidelines and not as absolute cutoff points. Arterial pressures apply to patients who were previously normotensive and should be adjusted upward for patients who were previously hypertensive. (RVFP and LVFP = right and left ventricular filling pressure.) ... 

In addition to their diuretic activity, loop agents appear to have direct effects on blood flow through several vascular beds. Furosemide increases renal blood flow. Furosemide and ethacrynic acid have also been shown to reduce pulmonary congestion and left ventricular filling pressures in heart failure before a measurable increase in urinary output occurs, and in anephric patients. 

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