Page 29, CV Review, Essentials, Develop. Physiol., Dr. D. Penney

Misconception 30. The Valsalva maneuver is a military exercise

Named for the early 18th Century anatomist, Antonio M. Valsalva, the Valsalva maneuver involves forcing against a closed glottis or mouth (Figure 1.12). It is used diagnostically to differentiate between subaortic stenosis (idiopathic hypertrophic subaortic stensosis, IHSS) and valvular or supra-aortic stenosis. The recovery phase response is abnormal in heart failure due to the inability of the heart to respond to increased preload.

During Phase I, left ventricle stroke volume and ejection fraction are augmented by the increased intrathoracic pressure which effectively lowers afterload. This raises blood pressure, reflexly depressing heart rate, but this lasts only a few seconds. In Phase II, cardiac venous return is decreased, reducing ventricular preload, hence stroke volume and blood pressure, which reflexly raises heart rate. This phase may continue for many seconds, with both the hypotension and the tachycardia becoming progressively more extreme. Hypotension and tachycardia are present at this time despite the fact that the Valsalva maneuver also involves breath-holding, which usually produces opposite changes in blood pressure and heart rate (see below).

Phase III of the Valsalva maneuver occurs after the glottis or mouth is opened and the first breath is taken. Blood surges into the right heart, fills the expanding lung vasculature, but return to the left heart is slow. Consequently, left ventricle stroke volume remains low and systemic hypotension continues. Only when normal breathing resumes, in Phase IV, do blood pressure and heart rate renormalize. During this period, arterial pulse pressure becomes very wide, indicative of the large stroke volume resulting from the supra-normal left ventricular filling which occurs as pent-up venous blood returns to the heart. Fainting (syncope) due to cerebral ischemia may occur during Phases II or III, when hypotension is most extreme. The Valsalva maneuver should be attempted with caution in persons with coronary artery disease.

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