What is Pericarditis?

Tim | July 8, 2011

Pericarditis

Pericarditis is inflammation of the pericardium, a membrane that surrounds the heart and its major blood vessels.

Pericarditis can be caused by:

infection
heart attack
autoimmune disorders
chest trauma
cancer
kidney failure
drugs

Pericarditis most often affects men aged 20-50. Pericarditis may be acute or chronic. Heart attack (see post-MI pericarditis) and myocarditis can cause pericarditis, as can radiation therapy to the chest and medications that suppress the immune system. Acute pericarditis due to tuberculosis begins insidiously, sometimes without obvious symptoms of lung infection.

It may produce fever and symptoms of heart failure, such as weakness, fatigue, and difficulty breathing. Cardiac tamponade may occur. Pericarditis can be misdiagnosed as myocardial infarction, and vice versa. Pericarditis is more common in adolescents and young adults. In a recent study, Merce et al found no difference in etiology, clinical course, and prognosis between elderly and younger patients with moderate and large pericardial effusions.

Pericarditis occurs in up to 15% of patients who have acute myocardial infarctions (heart attacks). There is also a late form of post-heart-attack pericarditis, called Dressler’s syndrome, that occurs weeks to months after the heart attack. Chronic pericarditis occurs when the pericardial inflammation does not resolve within a few weeks. Constrictive pericarditis occurs when a chronically inflamed pericardial sac sticks to the heart muscle, squeezing it constricting it. A CT or MRI scan can also help to diagnose chronic or constrictive pericarditis, by showing the thickening of the pericardial lining associated with these conditions. Potential sources of cardiac perforation include central line placement, pacemaker insertion, cardiac catheterization, sternal bone marrow biopsies, and pericardiocentesis.

Pericarditis usually occurs in flare-ups, but it may be the presenting manifestation. Constrictive pericarditis is a very difficult therapeutic problem. Diuretics may be used to remove excess fluid accumulated in the pericardial sac. Bacterial pericarditis must be treated with antibiotics. Fungal pericarditis is treated with antifungal agents. Medicines, such as aspirin, ibuprofen, or other nonsteroidal anti-inflammatory drugs (NSAIDs), are commonly used to manage the pain and inflammation. Acute inflammatory pericarditis usually lasts one to three weeks and doesn’t lead to further problems. About 20 percent of pericarditis patients have a recurrence within months or, rarely, within years. Pericarditis is treated with bed rest, diuretics, and digitalis, but definitive treatment requires surgery to strip the thickened pericardial lining from the heart.

Treatment for Pericarditis

Analgesics or anti-inflammatory drugs are given to relieve pain.
Antibiotics are also prescribed if the pericarditis is due to a bacterial infection.
Tamponade is treated by draining the fluid from the pericardial sac, usually via a tiny catheter.
Removing the fluid relieves the pressure on the heart, and restores normal cardiac function almost immediately.
Pericarditis is treated with bed rest, diuretics, and digitalis.
The right atrial deflection precedes the left, as one would expect from the discussion above. The P wave, then, is the electrical summation of these two component parts.

The QRS Complex (Ventricular Depolarization)

The QRS complex reflects depolarization of the interventricular septum and both ventricles. Normally, the electrical activation of this portion of the heart proceeds from the AV node to the inferior and left side of the interventricular septum. The septal depolarization from left to right, in a superior direction, is the first (earliest) event in the QRS complex; it represents the Q wave seen in the left precordial (chest) leads of the normal ECG. The remainder of the QRS deflection reflects depolarization of the right and left ventricles.

The nomenclature of this wave form can be confusing:

A Q wave refers to an initial negative deflection.

An R wave is the first positive deflection.

An S wave is a negative deflection following a positive deflection.

The size, axis, and configuration of the QRS complex are useful for the diagnosis of ventricular hypertrophy.

The T Wave (Ventricular Repolarization)

Normally, the T wave axis is similar to the QRS axis because of two cellular electrical factors: cellular repolarization causes a deflection opposite in direction to cellular depolarization, but ventricular repolarization occurs in a sequence opposite to that of depolarization. Therefore, although the direction of repolarization is opposite to that of depolarization, the cellular (and, therefore, ECG) electrical forces are reversed, resulting in a T wave axis similar to that of the QRS complex.

The PR Interval

The interval in time between the onset of the P wave and the onset of the QRS complex is termed the PR interval.

The PR interval varies with both age and heart rate. The higher the heart rate, the shorter the PR interval; for a given rate, the younger the age, the shorter the PR interval. A short PR interval suggests aberrant atrial to ventricular conduction.

The QT Interval

The interval between the onset of the QRS complex and the end of the T wave is referred to as the QT interval.

The QT interval is affected by heart rate, shortening normally at more rapid rates and lengthening at slower rates. For this reason, the QT interval is best “corrected” for rate, by referencing it to a rate of 60 bpm. This is done by dividing the absolute QT interval by the square root of the interval in seconds between R waves (that is, the cycle length).

The QT interval is modulated by the autonomic nervous system, and affected by a variety of electrolyte, mineral, and acid-base disorders.