Systolic Murmurs - Aortic Stenosis
One of the most frequent pathologic systolic murmurs is due to aortic stenosis. Most commonly, aortic stenosis arises from one of three conditions. A patient may be born with a congenital stenosis, or acquire the stenosis from secondary conditions such as rheumatic heart disease or idiopathic calcification of the valves. Persons born with an abnormal bicuspid valve are particularly susceptible to calcification later in life.
The murmur of aortic stenosis is typically a mid-systolic ejection murmur, heard best over the “aortic area” or right second intercostal space, with radiation into the right neck. This radiation is such a sensitive finding that its absence should cause the physician to question the diagnosis of aortic stenosis. It has a harsh quality and may be associated with a palpably slow rise of the carotid upstroke. Additional heart sounds, such as an S4, may be heard secondary to hypertrophy of the left ventricle which is caused by the greatly increased work required to pump blood through the stenotic valve. Because the second heart sound is largely generated by the sudden closing of the aortic valve, a poorly mobile and stenotic aortic valve may cause S2 to become quieter or even absent. Although S2 is normally created by the closure of the aortic valve followed by the pulmonary valve, if the closure of the aortic valve is delayed enough, it may close after the pulmonary, creating an abnormal paradoxical splitting of S2.
Aortic stenosis is a progressive disease, with typical symptoms and clinical findings to match its course. A good mnemonic to remember the march of symptoms related to undiagnosed aortic stenosis is ASC, or Aortic Stenosis Complications. One of the early symptoms is Angina, which is usually stable and exertion-related. A more serious and later condition is Syncope, again associated with exercise. Finally, the hypertrophied left ventricle can no longer meet demands, and Congestive heart failure may ensue. On examination, the phase during systole at which the murmur peaks can help to determine the severity of the disease. An early-peaking murmur is usually associated with a less stenotic valve, while a late-peaking murmur has a more severe degree of stenosis. This is because a more stenotic valve takes longer for the ventricle to generate the terrific pressures needed to force the blood past the lesion.