There is an increasing number of patients with presentation consistent with a heart attack but have no significant blockage of heart arteries. By Michael Lim
IN the last week, two patients were admitted with similar symptoms and findings consistent with a heart attack but had different underlying causes for their heart problems. They were both admitted to the hospital’s intensive care unit on the same day with shortness of breath.
Madam A was an independent and active octogenarian who had been having mild exertional breathlessness for a month and had suddenly become extremely breathless on the day of admission. A chest X-ray revealed water in her lungs and her blood oxygen level was low. Mr B was in his 50s and had found himself increasingly breathless over the last week and had neck tightness on exertion on the day of admission to the hospital. Blood tests for troponin, a heart muscle protein released during damage of the heart muscle, was significantly elevated in both. The 12 lead electrocardiogram (ECG) for both showed changes consistent with damage to the heart muscle. That is where the similarity ended.
Both underwent an X-ray examination of the heart arteries, coronary angiogram, that involved putting a small plastic tube through the limb artery and injecting iodine based contrast to opacify the heart arteries so that they can be visualised under X-ray examination. Mr B had a significant narrowing of a large heart artery that was the underlying cause for his heart attack. Madam A did not have any significant blockage of the heart arteries.
Doctors are beginning to realise that there is an increasing number of patients with presentation consistent with a heart attack but have no significant blockage of the heart arteries. These patients have “diastolic dysfunction” which in layman’s terms means that the heart muscle is stiff and cannot relax properly.
The heart cycle is divided into systole and diastole. Systole is the part of the heart cycle where the left lower heart chamber (ventricle) contracts and pumps blood out of the ventricle to the body. Diastole is the part of the heart cycle where the left ventricle relaxes and allows oxygen enriched blood from the lung arteries to enter the left ventricle via the left upper heart chamber (atrium). In diastolic dysfunction, the heart muscle becomes stiff and cannot relax fully. This results in incomplete filling of the left ventricle and elevation of the pressure inside the ventricle. This makes it more difficult for blood from the lungs to flow into the heart and in severe cases, the resulting elevation of pressure in the lungs results in water being pushed into the lung spaces causing “diastolic heart failure”.
It is now estimated that almost half of the patients who are seen in the emergency department for sudden heart failure have “diastolic heart failure”. When these patients are stabilised and the heart failure has resolved, the ultrasound examination of the heart will usually show a “normal” heart pump function.
“Diastolic heart dysfunction” is fairly common among elderly women with some studies showing prevalence of up to 75 per cent of elderly women. Although it is less common in men, it nevertheless increases with age and studies have shown prevalence of 50 per cent in men older than 70.
The common presentation for patients with “diastolic dysfunction” is breathlessness. Hence, these patients will notice that their exertional exercise capacity has decreased and they tend to get breathless easily on activities which they could do comfortably in the past. Fortunately, the diagnosis of “diastolic dysfunction” is made quite easily with an ultrasound test of the heart (echocardiogram) where special parameters are applied to measure the stiffness of the heart.
High blood pressure is the most common cause of “diastolic dysfunction”. As the heart muscle ages and becomes stiffer, it is less able to tolerate stress. Abnormal rhythms that reduce the pump function of the atrium (such as “atrial fibrillation”, a type of abnormal heart rhythm that causes the upper chamber to beat so fast that it is virtually quivering and loses its pumping function), fast heart rate (reduces the time available for blood to fill the left ventricle), sudden increase in blood pressure, increased salt intake, excessive fluid consumption and insufficient blood flow to the heart muscles may stress the heart and precipitate “diastolic heart failure”.
The American College of Cardiology and the American Heart Association joint guidelines recommend that blood pressure control, heart rate control, blood volume reduction, and alleviation of insufficient blood flow to the heart muscle are the key goals when treating patients with “diastolic heart failure”.
Reducing stress on the heart can be achieved by lifestyle changes such as not smoking, optimal control of high blood pressure, management of heart artery disease, weight loss, salt reduction, and reduction of alcohol intake. When necessary, drugs that lower the heart rate or reduce hemodynamic stress on the heart may be useful.
As the population ages, “diastolic dysfunction” becomes an increasingly common problem which is often not recognised. Therefore, if you are more than 50 years old, have recent onset of exertional breathlessness and underlying high blood pressure, you may have “diastolic dysfunction”. Early diagnosis and taking appropriate preventive measures may avoid the precipitation of sudden “diastolic heart failure” which may be potentially life threatening.