Heart block is a problem with the heart's electrical system. The electrical impulse for the heart to beat starts in the top chambers of the heart and travels through a network of cells that relay the signal to the lower chambers of the heart, called the ventricles. With heart block, not all impulses are transmitted to the ventricles. In 3-to-1 heart block, three signals are sent, but only one makes it to the ventricles.
Diagnosis
Heart block comes in four varieties: first-degree heart block, which is usually asymptomatic; second-degree heart block type 1 and type 2; and third-degree heart block. A 3-to-1 heart block occurs in second-degree heart block type 2. A health care provider uses an electrocardiograph to diagnose heart block. An electrocardiograph tracing of a heartbeat consists of a P wave followed by a QRS wave and a T wave. In second-degree heart block type 2, the P wave does not always have a QRS behind it because the signal gets blocked. A 3-to-1 heart block is identified by the three P waves to one QRS.
Significance
Kathleen Ouimet Perrin, author of "Understanding the Essentials of Critical Care Nursing," describes second-degree heart block type 2 with a 3-to-1 conduction delay as uncommon. Physicians consider this rhythm to be very serious because it produces a slow ventricular rate which makes patients symptomatic. A 3-to-1 heart block can progress to third-degree, or complete heart block, which means no signals are reaching the ventricles, which is life threatening.
Causes
The National Heart Lung and Blood Institute reports that heart block may be a congenital defect present from birth. Commonly, heart block results from coronary artery disease. People who have a heart attack to the anterior wall of the heart often suffer second-degree heart block type 2 because a segment of the conduction system is located in this part of the heart. A heart attack in this area prevents normal blood flow to the cells of the conduction system. The loss of blood flow permanently damages these cells, and they can no longer transmit electrical impulses properly.
Symptoms
In 3-to-1 heart block, heart rate is very slow, causing low blood pressure and making patients feel weak, tired, dizzy and faint. Patients may feel the skipped heartbeats and become anxious.
Treatment
Treatment of 3-to-1 heart block consists of a pacemaker to regulate heart rate and rhythm. Unstable patients are those with irregular heart rhythms, low blood pressure, chest pain and shortness of breath who may require medication to speed up the slow heart rate until the pacemaker can be implanted.
References
- "Understanding Essentials of Critical Care Nursing"; Kathleen Ouimet Perrin; 2009
- National Heart Lung and Blood Institute: Heart Block
Member Comments