The Valsalva maneuver is a simple procedure that involves the patient exhaling forcefully against a closed airway, typically by closing the mouth, pinching the nose, and blowing as if trying to inflate a balloon. It is the maneuver used to help clear a clogged ear when flying or swimming deep underwater.
Interestingly, this maneuver can also help diagnose serious heart conditions like aortic stenosis or hypertrophic obstructive cardiomyopathy, a condition that often leads to sudden death in athletic young adults while exercising. Hypertrophic obstructive cardiomyopathy (HOCM) is a condition characterized by abnormal thickening of the heart muscle, specifically the interventricular septum, which can lead to obstruction of blood flow from the left ventricle to the aorta. Diagnosing HOCM can be challenging due to its complex presentation and the variability of its symptoms.
The valsalva maneuver induces specific physiological changes in heart rate, blood pressure, and blood flow, providing valuable insights into cardiac function. Specifically, valsalva causes a heart murmur to appear or worsen when HOCM is present. Valsalva causes a heart murmur to decrease in intensity in patients with aortic stenosis or mitral valve regurgitation. A heart murmur can be easily heard using a stethoscope when listening to the heartbeat.
How the valsalva maneuver affects the heart consists of four distinct phases:
Phase I: As the patient starts to blow, there is an immediate increase in intrathoracic pressure, leading to a brief rise in blood pressure due to compression of the thoracic aorta.
Phase II: The continued strain reduces venous return to the heart, decreasing cardiac output and causing a drop in blood pressure. The heart compensates by increasing heart rate.
Phase III: After the strain is released, intrathoracic pressure drops suddenly, leading to a brief decrease in blood pressure.
Phase IV: Venous return increases rapidly, resulting in a rise in blood pressure above baseline, and the heart rate normalizes.
In patients with hypertrophic obstructive cardiomyopathy, the thickened interventricular septum can obstruct blood flow during systole (heart contraction). This obstruction becomes more pronounced when the size of the left ventricular cavity is reduced. The Valsalva maneuver, particularly during Phase II, significantly reduces venous return, causing the left ventricle to shrink slightly. In patients with HOCM, this reduction in left ventricular volume worsens the obstruction and amplifies an outflow murmur that can be heard while listening to the heartbeat with a stethescope. Here’s how it works:
Exacerbation of Left Ventricular Outflow Obstruction: During the Valsalva maneuver, the reduced venous return and subsequent decrease in preload (the volume of blood returning to the heart) cause the left ventricular cavity to become smaller. In individuals with HOCM, this reduced ventricular size brings the thickened septum closer to the mitral valve, increasing the obstruction of blood flow from the left ventricle to the aorta.
Amplified Systolic Murmur: One of the hallmark signs of HOCM is a systolic ejection murmur, caused by the turbulent flow of blood through the narrowed left ventricular outflow tract. As the obstruction worsens during the Valsalva maneuver, this murmur becomes louder and more pronounced. Clinicians listen for the murmur during and after the strain phase (Phase II) of the maneuver, and an increase in intensity strongly suggests HOCM.
While the Valsalva maneuver is a valuable clinical test, it has a sensitivity of 40-80% and specificity of 100%. As such, the definitive diagnosis of HOCM is usually confirmed through echocardiography, which provides detailed images of the heart's structure and function. Echocardiography can show the characteristic thickening of the ventricular septum and assess the degree of obstruction. Doppler imaging during echocardiography may also be used to evaluate the severity of the outflow tract obstruction and confirm the findings observed during the Valsalva maneuver.
References:
Hypertrophic Cardiomyopathy Is Predominantly a Disease of Left Ventricular Outflow Tract Obstruction. Circulation. Volume 114, Number 21. 2006Standardized Goal-Directed Valsalva Maneuver for Assessment of Inducible Left Ventricular Outflow Tract Obstruction in Hypertrophic Cardiomyopathy. Journal of the American Society of Echocardiography. Volume 31, Issue 7, July 2018, Pages 791-798.
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