Final answer:
The Valsalva maneuver may decrease preload and stroke volume in HCM patients, initially increasing afterload but subsequently lowering systemic resistance and briefly enhancing cardiac output upon release. Calcium channel blockers are often used to treat HCM symptoms by reducing ventricular contraction strength and SV, thereby lessening the obstruction.
Step-by-step explanation:
The Valsalva maneuver, involving voluntary contraction of the abdominal muscles and diaphragm while closing the glottis, can have specific effects on patients with hypertrophic cardiomyopathy (HCM). Performing the Valsalva maneuver increases intra-abdominal pressure and can lead to a drop in venous return to the heart, thus decreasing preload. In the context of HCM, where there is already a reduced ventricular volume due to the thickened heart muscle, further reduction in preload can lead to a significant decrease in stroke volume (SV) and cardiac output.
Additionally, the Valsalva maneuver initially causes a transient increase in afterload due to a spike in intrathoracic pressure. However, as the strain phase continues, systemic vascular resistance decreases, which might initially be beneficial for patients with HCM by reducing the outflow tract obstruction. As the maneuver is released, there is a sudden drop in intrathoracic pressure leading to a rapid rise in venous return and a transient increase in cardiac output, which could exacerbate the obstruction in the hypertrophied ventricle.
Calcium channel blockers, which include dihydropyridine, phenylalkylamine, and benzothiazepine, are often prescribed to patients with HCM to manage symptoms such as angina. These medications work by decreasing the strength of contraction and SV, alleviating the obstruction caused by the thickened ventricular wall.
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