Grinkov suffered what is known as ventricular fibrillation. This inefficient and deadly quivering of the heart is one of several types of irregular heartbeats, or arrhythmias, that afflict the lower chambers, called the ventricles, of the heart. Not all arrhythmias are ventricular; some, for example, arise from the upper chambers of the heart.
Ventricular arrhythmias often occur in people with various forms of heart disease and, according to the American Heart Association, cause most cases of sudden cardiac death. But new drugs and devices show promise in curbing the number of deaths from this condition. These new treatments, approved by the Food and Drug Administration, include a longer-acting form of an antiarrhythmia drug, a wide availability of portable and implantable electrical devices that can spark a return to normal heart rhythm, and techniques for destroying heart tissue that triggers ventricular arrhythmias.
Heart of the Matter
Not much bigger than a fist, the human heart beats 100,000 times each day, sending about 2,000 gallons of blood coursing through vessels, which, laid end-to-end, would be long enough to circle the earth more than twice.
To carry out the vital task of pumping blood, the electrical timing of millions of heart cells must be exquisitely coordinated. Their timing sparks the heart to pump in a rhythmic, efficient fashion. When that coordination is disrupted, life-threatening ventricular arrhythmias result.
Each heartbeat normally starts in the upper right chamber of the heart, or right atrium. Here, a specialized bunch of cells called the sinus node, or pacemaker, sends an electrical signal. The signal spreads throughout the right and left atria and then travels along specific pathways to the lower chambers or ventricles. As the signal travels, the heart muscle contracts. First the atria (the upper right and left chambers) contract, pumping blood into the ventricles. A fraction of a second later, the ventricles contract in a squeezing motion, sending blood throughout the body. Each contraction is a heartbeat.
Ventricular arrhythmias occur when a group of heart cells in the ventricles triggers contractions out of sync with the normal rhythm established by the sinus node. A number of factors can prompt a ventricular arrhythmia, including stress, exercise, caffeine, tobacco, alcohol, amphetamines, tricyclic antidepressant drugs, and cough and cold medicines containing pseudoephedrine, as well as several drugs (such as diuretics and digitalis) used to treat various heart conditions.
Many types of heart disease also are associated with ventricular arrhythmias. Atherosclerosis, the buildup of plaque on artery walls, can reduce blood flow to heart tissue. That, in turn, can impede the transmission of electrical signals governing heart contractions. This can prompt groups of ventricle cells to generate their own "back-up" rhythm. In the extreme case of a heart attack, blood flow to specific parts of the heart muscle is completely blocked, and that heart tissue dies. If the affected area includes cells in the electrical pathways of the heart, arrhythmias ensue.
People with enlarged hearts or faulty heart valves also are prone to experiencing ventricular arrhythmias. Ventricular arrhythmias also commonly occur after heart attacks, heart infections, or heart surgery, or when the body is under severe physical stress from, for example, lack of oxygen, very low blood pressure, or major blood loss. They also are triggered by heart failure, surgery, and other conditions that cause abnormal blood and tissue concentrations of potassium, magnesium, sodium, or calcium. These minerals play key roles in triggering and conducting electrical impulses in the heart.
