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i am kind of confused. it says in goljan that when u inspire the murmur on the right side of heart increases. but to my understandig whn u inspire there is decreased amount of blood that is going to the right side of the heart thus decreasing cardiac output.
since there is decreased blood going to left heart, why do you get increased murmur on inspiration.
Posts: 3,675,934
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ah guys just googled it...
my concept is clear now.
Mechanism of reduced blood pressure during inspiration in normal conditions
During inspiration, systolic blood pressure decreases slightly, and pulse rate goes up slightly. This is because the intrathoracic pressure becomes more negative relative to atmospheric pressure. This increases systemic venous return, so more blood flows into the right side of the heart. **However, the decrease in intrathoracic pressure also expands the compliant pulmonary vasculature. This increase in pulmonary blood capacity pools the blood in the lungs, and decreases pulmonary venous return, so flow is reduced to the left side of the heart. Reduced left-heart filling leads to a reduced stroke volume which manifests as a decrease in systolic blood pressure. The decrease in systolic blood pressure leads to a faster heart rate due to the baroreceptor reflex, which stimulates sympathetic outflow to the heart.
An alternative and more plausable explanation to the decrease in blood pressure during inspiration compared to the ** idea above, is that: A) increased negative intrathoracic pressure causes, B) increased right sided venous return, C) to the right atrium, and then right ventricle during diastole, D) which causes an increase in right ventricular filling pressures because of increased volume and stretch leading to E) a bulging of the intraventricular septum towards the left ventricle, F) decreasing the left ventricular size and filling volume, G) with subsequent decreased left sided stroke volume and therefore a lower systolic blood pressure. Note that this ventricular septal deviation from right to left can be visually seen during cardiac echocardiography real time and the decreased pressures can be measured.
