Diastolic heart failure
Diastolic dysfunction and diastolic heart failure occur as a result of deterioration in performance of one or both of the two lower chambers of the heart (the ventricles) during diastole. Diastole is the stage in which the heart relaxes and fills with blood from the venae cavae and pulmonary veins to the upper chambers, the left and right atria. Typically asymptomatic in early stages, diastolic dysfunction is detectable by echocardiography.
Definition & Facts
The human heart has four chambers. The upper two atria receive incoming blood flow; the lower ventricles pump it out. The cardiac cycle starts with spent, deoxygenated blood entering the right atrium from the venae cavae.
From the upper right chamber, this blood pours into the right ventricle, which pumps it into the pulmonary artery to the lungs for reoxygenation, revitalization, renewal, and reuse by all body systems. Pulmonary veins return this blood to the heart into the left atrium, which passes it to the left ventricle, which pumps it out of the heart through the aorta into universal circulation.
Essentially, the right side of the heart pumps blood to the lungs while the left side pumps it to the rest of the body from head to toes. First the atria contract, then the ventricles contract in the systolic stage of the cycle, and then all four chambers relax and rest in diastolic stage. The disparity in distance traveled indicates how much greater systolic force the left ventricle must exert comparatively to the right ventricle.
Symptoms & Complaints
Respiratory problems with breathlessness, coughing, and rapid breathing (tachypnea) are chronic, common, and conspicuous. Physicians refer to the progressively severe breathing difficulties of diastolic heart failure as flash pulmonary edema for the fluid that accumulates in the lungs.
Precipitating medical stresses that can set off flash pulmonary edema are atrial fibrillation and other arrhythmic conditions, periods of hypertension (especially systolic elevations), and episodes of cardiac ischemia or insufficient blood supply. Flash pulmonary edema is a hallmark of diastolic heart failure, but less severe and more gradual breathing problems may beset patients as well.
The cardiac cycle has two parts: systole and diastole. During systole, the ventricles contract to eject blood from the heart into the arteries. During diastole, after they contract, the ventricles must relax to replenish their blood supply for the next systolic contraction. The left ventricle must fill to full capacity dependent on flexibility for optimal cardiac output.
Hypertension, high blood pressure, is a frequent factor in the stiffening of ventricular tissue, particularly from stenosis or narrowing of the aorta, the major artery. Aortic valve stenosis from deposits of plaque on arterial walls increases hypertension because the blood must move faster through ever-narrowing space available for its circulation. This need for a faster flow compels the heart to beat at a faster rate to maintain the same amount of blood in circulation, straining and eventually stiffening the cardiac musculature.
Diagnosis & Tests
A definite diagnosis of diastolic dysfunction can be elusive because, after the condition of a patient with suspected diastolic heart failure stabilizes, cardiac performance can seem to be normal without a specific examination for the condition. Diastolic heart failure features a stiffened left ventricle with impaired flexibility for total tissue relaxation leading to chronic hypertension as the heart struggles to supply enough blood for normal body processes.
The diagnosis of diastolic dysfunction is most reliable with the aid of Doppler echocardiography, which uses ultrasound technology to determine the speed and direction of blood flow as shown on an echocardiagram. Use of the Doppler can assess the direction and velocity of blood flow at any point.
Velocity data can allow assessment of heart valve functions, detect abnormal communications between left and right sides of the heart, observe valvular regurgitation, blood leaks through the valves, and calculate cardiac output and the ratio of early to late ventricular filling velocities: a measure of diastolic dysfunction.
Treatment & Therapy
Diastolic dysfunction is a chronic condition. If well-tolerated by the patient, no special treatment may be necessary. In cases of advanced diastolic dysfunction to the point of incipient congestive heart failure, the initial treatment goal is to eliminate pulmonary congestion by lowering left ventricle volume, maintaining synchronicity in atrial contractions, and prolonging diastole by reducing the rapid heart rate.
Therapy should address hypertensive and diabetic causes of the impaired left ventricle. In the presence of atrial fibrillation, when rapid, irregular beats replace the normally rhythmic contractions of the upper chamber, there is no coordination, and the left ventricle loses up to 20 percent of its output. If atrial fibrillation persists, specific treatment must slow the morbidly rapid heart rate down to a stable rhythm.
Diuretics can help congestive patients, and beta blockers, drugs which manage cardiac arrhythmias (irregular heartbeats), are common therapeutic agents of induced bradycardia (slowed heartbeat rates) to allow time for ventricles to fill. There is some evidence that calcium channel blocker drugs, which can prevent the influx of calcium into smooth muscle of the heart, may be beneficial in ameliorating ventricular stiffness.
Prevention & Prophylaxis
Normal body weight, not smoking or quitting smoking, regular exercise, and a wholesome, nutritious diet can reduce heart failure risks associated with coronary disease, diabetes mellitus, and hypertension. This is because of the following risk factors:
- Being overweight and obesity. Recent data support the opinion that being overweight is predictive of heart failure.
- Exercise Habits. Physical inactivity is an important risk factor for heart failure. Conversely, regular, vigorous physical activity reduces risks of cardiovascular disease, hypertension, and diabetes. Walking is beneficial for primary prevention.
- Alcohol consumption. Excessive alcohol consumption and alcoholism invites alcoholic cardiomyopathy, disorder or disease of heart muscle tissue, yet there is also some evidence of benefit from moderate alcohol intake on the risk of heart failure, perhaps from relief from psychological stress.
- Dietary habits. Cardiologists encourage consumption of fruits and vegetables, grains and grain products, lean meats, fish, and poultry, and nuts, seeds, and legumes and advise against sugar and salt for those who eat meat, which supplies all salt necessary for health.
- Smoking. There is no safe level of tobacco smoke. All smokers should quit.