Diastole and Systole
A heartbeat is a two-part pumping action that takes about a second. The first part of the two-part pumping phase (the longer of the two) is called diastole. During diastole, blood collects in the ventricles.
After the ventricles fill with blood during diastole, the heart muscle contracts. This second part of the pumping phase is called systole. Blood travels from the right ventricle into the lungs to pick up oxygen at the same time that oxygen-rich blood travels from the left ventricle to the heart muscle and the rest of the body.
Diastolic dysfunction occurs when the ventricles cannot fill normally. In patients with certain types of cardiomyopathy and heart failure, the ventricles are unable to properly relax, and they become stiff. As a result, the ventricles may not fill completely, and blood can “dam up” in other parts of the body. The abnormal stiffening of the ventricles and the resulting abnormal ventricular filling during diastole is referred to as diastolic dysfunction. Internal ventricular pressure increases as blood from the next heartbeat tries to enter. The pressure “backs up” to produce fluid in the blood vessels of the lungs (pulmonary congestion) or the blood vessels leading back to the heart (systemic congestion). If left untreated, diastolic dysfunction can progress to diastolic heart failure.
Diastolic dysfunction is far more common than previously thought. Some echocardiographic studies found diastolic dysfunction in 15% of patients less than 50 years old, and in 50% of patients older than 70. Furthermore, up to 75% of patients with diastolic heart failure are women.
What Causes Diastolic Dysfunction?
Diastolic dysfunction itself often produces no symptoms unless it progresses to the point of causing diastolic heart failure.
Using echocardiography, diastolic dysfunction can be diagnosed in patients who have never had an episode of heart failure. An echocardiogram can assess the characteristics of diastolic relaxation and left ventricular “stiffness.” It can also reveal the cause of the diastolic dysfunction. However, many patients who show diastolic dysfunction on echocardiography have no other diagnostic findings.
An electrocardiogram (ECG) can be used to determine the presence of left ventricular muscle thickening, but it cannot determine its definite cause.
When an episode of symptomatic heart failure has occurred in a patient with a normal left ventricular ejection fraction, diastolic heart failure is diagnosed. It is possible that almost half of the patients who are seen in emergency rooms with acute episodes of acute heart failure actually have diastolic heart failure. The diagnosis of diastolic heart failure, unfortunately, is often missed because after the patient has been stabilized, the heart may appear entirely normal. It can be caught if the doctor looks specifically for evidence of diastolic dysfunction on an echocardiogram.
Diastolic dysfunction is treated by aggressively managing the underlying condition. Other treatment principles include:
- Aggressive control of both systolic and diastolic high blood pressure.
- Aggressive treatment of coronary artery disease (CAD). Undiagnosed and asymptomatic CAD is a potentially important cause of diastolic dysfunction.
- Careful management of atrial fibrillation, including aggressive attempts to restore a normal rhythm.
- Control of pulmonary congestion with diuretic medicines.
If no underlying cause for diastolic dysfunction is obvious, three things should be considered:
- Undiagnosed (or mild) high blood pressure: begin careful monitoring for it.
- Undiagnosed CAD: use exercise testing as a diagnostic tool.
- If possible, use aerobic exercise as a tool to improve diastolic function.
Diastolic dysfunction is a relatively “new” disorder; that is, until a few years ago, it was poorly recognized even by cardiologists. However, it is rapidly becoming well-known and is now one of the most common diagnoses made via echocardiogram.
In cases of diastolic dysfunction without symptoms, at least two studies have suggested that these patients have a higher mortality rate than normal. This finding is not surprising considering the underlying causes of diastolic dysfunction (i.e., high blood pressure and undiagnosed CAD).
In cases of diastolic dysfunction with symptoms, patients who have had an episode of diastolic heart failure have a somewhat better prognosis than patients with traditional (systolic) heart failure but a far worse prognosis than patients without heart failure or diastolic dysfunction. Given this relatively poor prognosis, patients should be aggressively evaluated and treated, even after acute episodes of heart failure have resolved.
Diastolic dysfunction is an important condition that, at the very least, should prompt a careful search for underlying causes. The increasing recognition of diastolic dysfunction should draw needed attention to the care of women who are prone to develop significant heart disease.
American Heart Association www.americanheart.org/presenter.jhtml?identifier=4558
About.com: Heart Disease http://heartdisease.about.com/od/livingwithheartfailure/a/diastolic_HF.htm
Texas Heart Institute www.texasheartinstitute.com/HIC/Topics/Cond/ddisfunc.cfm