6
Keeping pace
LIBIN LIFE
Understanding abnormal heart rhythms By Dr. Hailey Jansen, PhD
T
he heartbeat in a healthy individual is rhythmic and coordinated. Each heartbeat is initiated in the natural pacemaker region of the heart called the sinoatrial node. Electrical signals generated here are conducted from the upper chambers of the heart (the atria) to the lower (the ventricles). This allows these regions of the heart to contract and pump blood to the body. Disruptions in the pattern of conduction of these signals can lead to an irregular heartbeat, called an arrhythmia. Cardiac arrhythmias can cause the heart to beat too slow (called bradycardia), too fast (called tachycardia), with an irregular rhythm (called flutter or fibrillation), or cause an extra heartbeat. Arrhythmias may cause symptoms like dizziness, shortness of breath, palpitations and chest pain.
Types of Arrhythmias
The heart rate for healthy adults falls between approximately 60-80 beats per minute. If the heart rate drops below this point, the heart can’t pump enough blood to meet the body’s needs. Tachycardia, on the other hand, occurs when the heart beats too fast. It can impact the supraventricular or ventricular regions of the heart. Supraventricular arrhythmias are not usually life
between the upper and lower chambers of the heart. This means that both the rate and rhythm of the heart are impacted.
Causes and treatment
threatening but can diminish a patient’s overall quality of life. Ventricular arrhythmias affect the lower chambers of the heart and can be life threatening. Ventricular fibrillation (VF) leads to rapid and ineffective ventricular contractions that prevent the ventricles from pumping blood to the body. Patients with VF require immediate medical attention to shock the heart back into normal rhythm, as the condition can be fatal within minutes. The most common sustained cardiac arrhythmia is atrial fibrillation (AF). When the heart is in AF, the atria quiver at rates exceeding 400 beats per minute due to highly disorganized patterns of electrical conduction travelling within the atria. Some, but not all, of these electrical signals travel from the atria to the ventricles, resulting in uncoordinated contractions
Researchers know that cardiac arrhythmias are caused by alterations in the structure and electrical function of the heart. These changes can be inherited, induced by certain medications, or occur in conjunction with different diseases. Patients with heart attacks, for example, can be more susceptible to developing arrhythmias. Given the potential danger and loss of quality of life associated with arrhythmias, researchers at the Libin Institute are investigating the specific causes and possible treatment of a number of arrhythmias with the goal of improving patient outcomes. Fortunately, arrhythmias are often treatable. While the treatment depends on the specific type of arrhythmia, common therapies include healthy lifestyle choices, medications, or surgical procedures such as ablation. Implanted devices like pacemakers and defibrillators may also be used. Dr. Hailey Jansen is a postdoctoral fellow in the lab of Dr. Robert Rose, PhD.
