Classes of Cardiomyopathies for the Physician Assistant Exam
A good understanding of cardiomyopathy is useful for the Physician Assistant Exam. A cardiomyopathy is an abnormality of heart function secondary to changes in the structure of the heart muscle. The most common cause of congestive heart failure is an ischemic cardiomyopathy.
Note that in many if not all cases, you can make the diagnosis by an echocardiogram interpretation (in addition to a history and physical). Often, a cardiac catheterization has to be done to rule out coronary artery disease (CAD) as a cause of the cardiomyopathy.
The three classifications of cardiomyopathy you need to be familiar with are dilated, restrictive, and hypertrophic.
If you look at a dilated cardiomyopathy (DCM) on an echocardiogram, you’ll likely see dilatation of both atria and both ventricles. Basically, the heart becomes weakened and enlarged and can’t pump blood very well. The common causes of dilated cardiomyopathy include long-term alcohol consumption, viruses, and certain medications. For example, the antineoplastic agent doxorubicin (Doxorubicin) and the monoclonal antibody trastuzumab (Herceptin) can be causes of a dilated cardiomyopathy.
The most common initial presenting symptoms are those of CHF, and dilated cardiomyopathy is diagnosed by echocardiogram. The mainstay of treatment is removing the offending agent (for example, stopping drinking) and using ACE inhibitors and beta blockers together.
Restrictive cardiomyopathy (RCM) refers to a condition in which the heart’s walls are rigid, limiting the heart’s stretching and filling with blood. The most common causes of restrictive cardiomyopathy are the infiltrative conditions, and examples of common infiltrative conditions include amyloidosis and sarcoidosis.
Hypertrophic cardiomyopathy (HCM) commonly occurs in young people. The typical scenario is the young person who has a syncopal episode during an athletic event. This condition can cause death.
Hypertrophic cardiomyopathy can be genetically inherited, usually in an autosomal dominant manner. The diagnosis is made by the history and physical exam findings and is confirmed by echocardiogram. Here are some key points concerning a hypertrophic cardiomyopathy:
On physical examination, the murmur increases with the Valsalva maneuver, because you’re decreasing the amount of blood going into the left ventricle.
On the PANCE, a physical examination question may want you to differentiate between the murmur accompanying a hypertrophic cardiomyopathy and the murmur accompanying aortic stenosis (AS). In aortic stenosis, the murmur decreases with the Valsalva; this is the direct opposite of hypertrophic cardiomyopathy. However, both conditions have a midsystolic ejection murmur.
The medical treatment for hypertrophic cardiomyopathy can include the use of beta blockers and calcium channel blockers to relax the left ventricle.
Surgical treatment can include a surgical myomectomy in which part of the interventricular septum is shaved. Alcohol septal ablation has also been used in the treatment of this condition.
Because hypertrophic cardiomyopathy carries with it an increased risk of sudden death, it’s recommended that an implantable cardioverter defibrillator (ICD) be placed in someone with this condition, especially if he or she has a strong family history of sudden death.