Ask The Doctors: February 2015
Q. I was recently in a rehab center following some complications after hip replacement surgery. I found out that my blood pressure was spiking in the middle of the night. I started taking a diuretic for mild hypertension a year ago. Is it normal for blood pressure to go up (it was around 170/90 at times) during the night and come down during the day? If not, what might be causing this?
A. I’m glad you brought this up, because what you are experiencing is not considered normal. Round-the-clock blood pressure (BP) measurement performed outside of the clinic or hospital, known as ambulatory BP monitoring (ABPM), has demonstrated that in most people BP drops by 10-20 percent during sleep, a pattern known as “normal dipping.” Individuals with the opposite pattern—those who experience a BP rise while sleeping—are referred to as “reverse dippers.” A large Israeli study published in 2007 of approximately 4,000 patients referred for ABPM revealed that reverse dippers had almost double the mortality risk of normal dippers, even after adjustment for other variables. Another study showed that reverse dippers were at higher risk for heart attack, stroke, and death from any cause, when compared to normal dippers.
These observations raise justifiable concerns. The exact cause of the reverse dipping pattern is not known, but one possibility is that despite taking the diuretic, you are still experiencing volume overload from accumulation of too much sodium and water. If so, your doctor may choose to alter your anti-hypertensive regimen (for example, with addition of a more potent diuretic). Kidney dysfunction can also lead to an abnormal dipping pattern. Another proposed mechanism for reverse dipping is activation of the sympathetic nervous system, leading to high adrenaline (epinephrine) output at night. Since this can sometimes be the result of obstructive sleep apnea, I would suggest that you talk to your doctor about getting a sleep study. Other situations associated with abnormal dipping are when the body secretes excess levels of the hormones cortisol, aldosterone, or epinephrine into the blood. Since your measured BP of 170/90 is considered Stage II hypertension by our latest set of treatment guidelines, it is important that this issue be addressed soon to reduce the likelihood of cardiovascular complications.
Q. I’ve heard that if you have blockage in one artery, you may have it in other arteries. I have two stents in my heart, but when I see my cardiologist for checkups, he doesn’t check my carotid arteries or look for peripheral artery disease. What should a heart patient’s exam include?
A. What you’ve been told is partially correct. Atherosclerosis (cholesterol plaque buildup and inflammation) in one arterial system—for example, the coronary arteries—increases the probability of having it in other systems, such as the cerebrovascular arteries (which include the carotids) or the peripheral arteries supplying the limbs. However, at present no data exist to support doing routine imaging tests to screen for carotid or peripheral artery disease. In fact, it is more likely that overperformance of such tests would actually increase the risk of harm to patients (by triggering unnecessary invasive testing), rather than helping them. The most important single element when visiting your doctor is discussing your symptoms, which would include neurological abnormalities (suggesting transient ischemic attack or stroke) or claudication in the legs (suggesting narrowing in the peripheral arteries). As for the yearly physical examination, in addition to listening to the heart and lungs, it should include palpation (feeling) of pulses in the arms and legs, and listening for bruits (abnormal sounds) over the carotid arteries and femoral arteries. Although not particularly sensitive for detecting narrowings, bruits, once they are heard, can be the tip-off for finding a severely narrowed vessel.