eCardioVascular Beat

Apnea can cause patients to lose more than sleep

Emilia Arden, D.O., F.A.C.C.

Cardiologist, Providence St. Vincent Medical Center
Northwest Cardiologists

Sleep is supposed to be restorative, a time for our body to heal and recharge. Yet over years of studying the phenomenon of sleep, we have learned that there are many patients who have very distorted sleep patterns.

If these disturbances go undiagnosed and untreated they can lead to other medical conditions such as refractory systolic hypertension, edema, weight gain, congestive heart failure (systolic and diastolic), atrial and ventricular arrhythmias, pulmonary hypertension and disabling fatigue.

How does this develop? Weight gain is a primary contributor to many patients who develop sleep disorders such as snoring, hypopnea, apnea, hypoventilation and hypoxia. Instead of getting restful, rejuvenating sleep, many patients are in a state of continual physical stress.

As hypopnea, apnea or snoring cause oxygen levels to decrease during sleep, the pH of the blood also decreases. This decrease in pH is perceived by the kidney as abnormal. In an attempt to restore the pH to a physiological level, the kidney retains more sodium (Na+) and therefore more water in exchange for elimination of CO2 as a bicarb product. Through this process the patient may have an increase in blood pressure and edema, which are difficult to treat with medication only.

We frequently encounter patients who experience symptoms of acute heart failure, unstable angina or arrhythmia occurring primarily at night. These patients often have a difficult time losing weight despite trying various weight-loss methods. In these patients a significant portion of their weight is fluid that accumulates due to their sleep apnea phenomenon.

In addition to fluid retention, the brain perceives nocturnal hypoxia as a generalized shock and creates a neurohormonal storm to awaken the person. The neurohormonal state can cause a number of cardiac arrhythmias, from atrial fibrillation as the most common to heart block, ventricular tachycardia and ventricular fibrillation. Even death can result.

Untreated apnea can speed heart failure

Since most patients who suffer from sleep apnea are overweight, they also have some degree of myocardial diastolic dysfunction at baseline.

When there is an increase in blood pressure or heart rate at night due to an apnea spell, these patients are unable to accommodate the changes and will develop acute exacerbation of heart failure.

It is harder to diagnose their condition as heart failure since most of them have a normally functioning heart and the lab we use to screen for heart failure (BNP) is usually only mildly elevated.

Their heart muscle is pumping well, but it is stiff and cannot relax, and any mild increase in heart rate is perceived as shortness of breath. The BNP in this group of patients is being cleared not only through their kidneys, but also through body fat.

Over time, if these patients are not identified and treated appropriately, they may present with overt biventricular heart failure, the most common atrial fibrillation, with fast ventricular response and generalized edema. Heart failure is the result of long-standing high blood pressure and fast heart rate called hypertensive and tachycardic cardiomyopathy.

Many patients who suffer from sleep apnea die from arrhythmias in their sleep at a young age. Other patients may develop pulmonary hypertension and valvular disease due to chronic elevated intracardiac pressure associated with sleep apnea. Holter monitors show that these patients frequently have bursts of atrial arrhythmia at night, and nocturnal oxymetry will display frequent episodes of hypoxia and tachycardia.

Screening for sleep apnea is extremely important since correcting the sleep pattern can alleviate many of the cardiovascular conditions precipitated by this phenomenon.