Premature Ventricular Contractions (cont.)

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How is premature ventricular contraction diagnosed?

There are two aspects in the diagnosis of premature ventricular contractions -- detecting them and diagnosing the underlying causes. Electrocardiograms (EKGs) and Holter monitors are used to diagnose premature ventricular contractions. EKGs, blood tests, echocardiograms, and cardiac stress tests are used to determine the underlying causes of premature ventricular contractions.

Electrocardiogram (EKG)

An electrocardiogram (EKG or ECG) is a brief recording of the heart's electrical discharges. EKGs can be performed in the doctors' offices, clinics, and hospital emergency rooms. Doctors frequently ask for a rhythm strip (a prolonged EKG recording) to be performed at the same time as an EKG to increase the chances of detecting premature ventricular contractions and other abnormal rhythms. The premature ventricular contractions are easy to recognize on EKG and rhythms strips, provided premature ventricular contractions occur during the recording. EKG may also demonstrate other problems such as heart attacks, hypokalemia, digoxin toxicity, and heart muscle thickening (hypertrophy) due to long term high blood pressure.

Holter monitor

A standard EKG and a rhythm strip performed at the time of a visit to the doctor's office may not detect the premature ventricular contractions because they may not be occurring at that moment. Holter monitoring is then necessary to detect the premature ventricular contractions in these patients with heart palpitations. A Holter monitor is a continuous recording of the heart's rhythm for 24 hours. Holter monitoring can be used diagnose premature ventricular contractions as well as other heart rhythm abnormalities such as atrial fibrillation, atrial flutter, and ventricular tachycardias.

PVCs are present in more than 6% of middle-aged adults. PVCs can be demonstrated during Holter monitoring. However, not all premature ventricular contractions found during Holter monitoring are clinically important. Doctors interpreting the Holter monitoring studies must take into account the patient's medical history in determining the importance of Holter monitor findings.

In patients with infrequent symptoms an event marker may be used in lieu of a Holter monitor as this can be worn for up to 30 days.

Echocardiography

Echocardiography uses ultrasound waves to produce images of the heart's chambers and valves and the lining around the heart (pericardium). Echocardiography is useful in measuring the size of the heart chambers, the forcefulness of heart ventricle contractions, the thickness of the heart muscles, and the functioning of the heart valves. Echocardiography is therefore useful in diagnosing conditions that can cause premature ventricular contractions such as:

  • Mitral valve prolapse: Echocardiography can detect and measure the severity of mitral valve prolapse and other valvular diseases.
  • Muscle hypertrophy: Echocardiography can detect heart muscle hypertrophy (thickening of heart muscle) as a result of long-term high blood pressure.
  • Heart muscle damage: Echocardiography can measure the extent of heart muscle damage from heart attacks or cardiomyopathy.
  • Ejection fraction: Echocardiography can be used to calculate the ejection fraction of the left ventricle. Ejection fraction is a measure (estimate) of the amount of blood pumped during each contraction of the ventricle. Heart ventricles extensively weakened by heart attacks or cardiomyopathy will have low ejection fractions. Patients with low ejection fractions have higher risks of developing life-threatening ventricular tachycardias and fibrillations than patients with normal ejection fractions.

Exercise cardiac stress test (treadmill stress test)

Exercise cardiac stress testing (ECST) is the most widely used cardiac stress test. The patient exercises on a treadmill according to a standardized protocol with progressive increases in the speed and elevation of the treadmill (typically changing at 3-minute intervals). During the ECST, the patient's electrocardiogram (EKG), heart rate, heart rhythm, and blood pressure are continuously monitored. If a coronary arterial blockage results in decreased blood flow to a part of the heart during exercise, certain changes may be observed in the EKG, including increases in premature ventricular contractions and development of ventricular tachycardias.

Adjuncts to ECST (stress echo and nuclear imaging)

Another supplement to the routine ECST is stress echocardiography. During stress echocardiography, the sound waves of ultrasound are used to produce images of the heart at rest and at the peak of exercise. In a heart with normal blood supply, all segments of the left ventricle (the major pumping chamber of the heart) exhibit enhanced contractions of the heart muscle during peak exercise. Conversely, in the setting of cardiovascular disease, if a segment of the left ventricle does not receive optimal blood flow during exercise, that segment will demonstrate reduced contractions of heart muscle relative to the rest of the heart on the exercise echocardiogram. Stress echocardiography is very useful in enhancing the interpretation of the ECST, and can be used to exclude the presence of significant cardiovascular disease in patients suspected of having a "false-positive" ECST. Alternatively, nuclear imaging may be used as an adjunct to ECST and may be even more sensitive in noninvasively detecting underlying coronary artery disease.

Blood tests in diagnosing causes of premature ventricular contractions

Blood tests for diagnosing conditions that can cause premature ventricular contractions include:

  • blood electrolyte levels can be performed to detect low potassium or magnesium levels (hypokalemia and hypomagnesemia);
  • blood drug levels can be performed to detect digoxin and aminophylline drug toxicity or thyroid levels, for example, an overactive thyroid may result in premature ventricular contractions;
  • blood oxygenation (oximetry) can be measured to detect hypoxia;
  • blood tests can be performed to detect illicit drugs, such as amphetamine abuse; and
  • blood levels of cardiac enzymes (creatine phosphokinase [CPK], troponins [regulatory proteins]) can be performed to assess for heart muscle damage as a result of heart attacks.
Medically Reviewed by a Doctor on 11/13/2013

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