Reflections on the Changing Aspects of Aortic Stenosis in the 21^st Century

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When I was a medical student 40 years ago, aortic stenosis was almost always the result of rheumatic heart disease. These days, rheumatic aortic valve disease has nearly vanished in the US. However, aortic stenosis is still quite common on the wards of our hospitals. What accounts for this change in valvular heart disease etiology, and why is aortic stenosis now so common?

The answer to the questions just posed is 2-fold: aortic stenosis in 2009 is the result of congenital bicuspid aortic valves and atherosclerotic/calcific aortic valves. Approximately 1% of all infants born alive in the US have bicuspid aortic valves. Mechanical stress distributed abnormally across the 2 cusps of these bicuspid valves causes them to “wear out” earlier than expected. Thus, many individuals with bicuspid aortic valves develop clinically important aortic stenosis during late middle life sometime between the 5^th and 6^th decades. Atherosclerotic/calcific aortic stenosis, on the other hand, develops later in life and is a manifestation of diffuse atherosclerosis that commonly affects elderly Americans. This lesion usually becomes clinically important when the patient is around age 80 years or older. Because these elderly patients often have a number of co-morbid conditions, the presence of aortic stenosis can present the clinician with a number of challenges, particularly in the setting of aortic valve replacement.

Because aortic atherosclerosis is exceedingly common in older Americans, it is not surprising that this process affects the aortic valve, whose endothelial lining is continuous with that of the aorta itself. Early atherosclerosis of the aortic valve can be detected during a routine physical examination: the characteristic early systolic aortic flow (aortic sclerosis) murmur usually heard best along the upper right sternal border should alert the clinician to the fact that this patient has aortic valve atherosclerosis that may eventually become clinically important atherosclerotic/calcific aortic stenosis over a number of years. Moreover, the presence of this aortic sclerosis murmur signifies that the patient in question also has atherosclerosis of the aorta itself and very likely atherosclerosis of other arteries, for example, the coronary or carotid arteries.

When atherosclerotic/calcific aortic stenosis becomes severe in an elderly patient, the decision for aortic valve replacement is often a difficult one. These patients frequently have concomitant fixed renal disease, obstructive pulmonary disease, cerebral atrophy, cerebrovascular disease, diabetes mellitus, and peripheral vascular disease. Age >80 years and the presence of these listed co-morbid conditions increases the risk for mortal or morbid events following aortic valve replacement. In most surgical series, aortic valve replacement in patients aged >80 years is associated with a mortality rate ranging from 8%-25%, depending on the patient's state of debility. In this setting, aortic valve replacement also is often accompanied by impressive morbidity, for example, stroke, myocardial infarction, pneumonia, postoperative delirium, or a prolonged catabolic state that may require many months of gradual rehabilitation before the patient is functional again.

Given these problems, how do I personally decide whether it is reasonable to consider aortic valve replacement in an elderly patient? My thought process proceeds in the following manner:

If the answer to questions 1 and 3 is yes, and the answer to questions 2 and 4 is no, then I recommend aortic valve replacement to the patient. I always warn the patient and their family members that the road ahead will have some “bumps” such as postoperative delirium and a prolonged and slow recovery period. However, once the patient reaches 6-12 months following the surgery, their energy level and their sense of well-being frequently increase as a result of the operation.

Over the years, I have taken dozens and dozens of elderly patients with aortic stenosis through aortic valve surgery, usually with very good outcomes. However, I believe that these good outcomes are partly the result of careful patient selection and partly the result of the excellent surgical technique of my thoracic surgical colleagues. One final note: I tell every one of these elderly individuals that they are “old enough to make up their own mind.” Even if I think they are good candidates for surgery, it is still their prerogative to opt for medical therapy only. A goodly number of patients, including my own father, have chosen the medical option over the years. Unfortunately, oral statin therapy has generally not been shown to slow or ameliorate the rate of progression of atherosclerotic calcific aortic stenosis.

In conclusion, aortic stenosis is a serious, relatively common condition in elderly Americans. It is often the result of diffuse atherosclerotic vascular disease. Aortic valve replacement can be offered to many of these elderly patients, and the outcomes from such operations are usually very good. However, careful patient selection and education are essential.

As always, I'd be interested in hearing your comments on this important topic. Feel free to send me an e-mail or post a comment on our blog, http://amjmedicine.blogspot.com.