Arrhythmias

What is an Arrhythmia?

Heart failure impairs both the heart muscle and the heart’s electrical system. Disturbances of the heart’s normal rhythm, which can manifest as arrhythmias – result from problems with the electrical system. Because of heart muscle damage, patients with heart failure commonly have arrhythmias, especially from the lower chambers of the heart (the ventricles) consisting of slow, fast, or irregular heart beats.

Management of arrhythmias in heart failure patients is a specialized field and requires the collaboration between arrhythmia and heart failure specialists. Some of the drugs made to suppress these rhythm disturbances can also decrease the heart’s pumping ability, which could worsen heart failure and in turn cause more arrhythmias. The goal of therapy is to treat the arrhythmia and the heart failure together.

Extra or rapid heart beats, called palpitations, are sometimes felt as “fluttering sensations” in the chest. Some people faint or feel dizzy or short of breath. Still others may feel chest pain or nothing at all when they have an arrhythmia. Generally, but not always, the longer the arrhythmia lasts, the more severe the symptoms.

Arrhythmias are divided into two main types, bradycardia (slow heart rates) and tachycardia (fast heart rates).

Bradycardia

A type of arrhythmia (abnormal heart rhythm) where the resting heart rate is slower than normal, or below 60 beats per minute. This is caused by the disruption of electrical signals that normally keep the heart beating at a steady pace.

A normal heart rate is between 60-100 beats per minute. The resting heart rate during sleep, and that of some athletes, sometimes falls below 60 beats per minute, but is not often considered abnormal.

During bradycardia, the heart rate is so slow that not enough blood is pumped throughout the body. This can result in fainting, dizziness, shortness of breath, or fatigue.

Tachycardia

A type of arrhythmia (abnormal heart rhythm) where the resting heart rate is faster than normal, or above 100 beats per minute.

During exercise or stress, the heart rate can rise above 100 beats per minute, but this is normal. Tachycardia that occurs when a person is at rest, and depending on the health status of the patient, may be harmful or life threatening.

Tachycardia may cause the heart to pump an insufficient amount of blood throughout the body, causing fainting, dizziness, shortness of breath, or fatigue.

Both bradycardia and tachycardia can be especially dangerous to someone with heart failure and a weakened heart muscle (cardiomyopathy). When the heart beats too slowly, too little blood is pumped out to the rest of the body. When the heart beats too quickly, it cannot fill completely so the body does not receive the blood volume it needs to function properly.

Arrhythmias are often diagnosed by cardiac exam, electrocardiogram (ECG), Holter monitor, event recorder, or an invasive examination of the heart called an electrophysiology study. After thoroughly examining you and determining that you do have an arrhythmia or are at high risk to develop one, the doctor may order one or more tests to determine the type of arrhythmia present, what may have caused it, and how to treat it.

Cardiovascular MRI

The USC Division of Cardiovascular Medicine is particularly proud of its pioneering program in high-field cardiovascular magnetic resonance (CMR) imaging. While most cardiac centers use lower-field imaging devices, our division has invested in devices capable of high-field diagnostic studies. With this novel technology, the heart can be captured in three dimensions with amazing clarity. Our two new 3T MRI systems produce optimal-resolution images of the heart muscle, the structure of the heart (for congenital and valvular heart disease detection), and the coronary arteries. They also allow us to observe scarred heart muscle, blood flow through the muscle of the heart, and heart muscle metabolism to detect and study inadequate blood flow to the heart. CMR additionally allows for clinical visualization of the peripheral and renal arterial systems as well as the carotid arteries. With CMR, conditions such as aortic aneurysms and aortic dissections can be detected at their earliest phases, and the presence and extent of pulmonary hypertension can be reliably determined.

USC cardiovascular medicine faculty are involved in several research projects that employ CMR imaging. Using CMR’s ability to accurately evaluate left ventricular size, shape, and function, USC acts as a core laboratory for the international NIH (NHLBI)-supported Surgical Treatment for Ischemic Heart Failure (STICH) trial, which examines surgical treatment for heart failure after heart attack. The STICH trial compares medical, bypass surgical, and surgical ventricular restoration. In a second NIH (NHLBI)-supported, CMR-based program, our researchers study the heart muscle in patients with type I diabetes. Using phosphorus CMR to assess ATP and phosphocreatine levels in the heart muscle at rest and during stress, the study aims to determine the biochemical basis for the abnormal heart function commonly found in diabetics. Finally, a third NIH (NHLBI)-supported program-the Women’s Ischemia Syndrome Evaluation (WISE)-uses phosphorus CMR at rest and with stress to determine the basis for chest pain in women who show no evidence of coronary artery obstruction. Many women suffer from this syndrome, sometimes called “Cardiac Syndrome X.”

CMR imaging is non-invasive and allows for the evaluation of heart and vascular function using a single modality and without the risks associated with ionizing radiation or X-ray dye. High-field CMR imaging can be described as a “one-stop shop” for the comprehensive analysis, including severity and prognosis, of virtually any form of cardiovascular disease.

Echocardiography

Echocardiography is now considered as important to office cardiology evaluations as electrocardiography has been for the past three decades. The USC Division of Cardiovascular Medicine has very active, state-of-the-art echocardiography laboratories both at USC University Hospital and the LAC+USC Medical Center. Many referring community physicians rely on the sophisticated echocardiogram assessments our cardiology experts provide.

Transthoracic echocardiogram (TTE): A transthoracic echocardiogram is essentially an ultrasound of the heart. During a TTE, a transducer wand is moved over the skin of the chest, taking images of the heart through the chest wall. This allows for the comprehensive evaluation of heart condition and function and for assessment of tumors, ischemia (inadequate blood flow), and viability. The stress echocardiogram, which combines a treadmill stress test and a transthoracic echocardiogram, is an indispensable tool for ischemia analysis.

Transesophageal echocardiogram (TEE): In some cases, a patient’s build or a pre-existing condition may limit ultrasound transmission, so that a transthoracic echocardiogram cannot be used. For these patients, a transesophageal echocardiogram can be used to evaluate the basic function of the heart. During a TEE, a transducer is attached to the tip of a thin, flexible tube and inserted down the throat and into the esophagus. TEE plays a major role in the comprehensive assessment of aortic disorders, systemic emboli, and the heart valves, especially for patients with mitral regurgitation, mitral stenosis, aortic stenosis, or tricuspid stenosis. TEE is also a very valuable tool in evaluating the function and pathology of prosthetic valves as well as assessing left atrial thrombi (blood clots). In select cases, a dobutamine TEE can be performed to evaluate for ischemia. Injecting a patient with dobutamine increases heart rate and blood pressure so that the heart can be studied under stress conditions.

The echocardiography program includes the following services:

• Comprehensive assessment of valvular and nonvalvular hemodynamics
• Contrast echocardiography
• Dobutamine stress echocardiography
• Dobutamine transesophageal echocardiography
• Exercise stress echocardiography
• Intraoperative echocardiography
• Myocardial dysynchrony imaging
• Three-dimensional echocardiography
• Tissue Doppler imaging
• Transesophageal echocardiography
• Transthoracic echocardiography

Electrophysiology

The USC Cardiac Electrophysiology Service offers specialized treatment to patients who are diagnosed with arrhythmias and/or heart failure. Our understanding of the processes that lead to heart failure enables us to take effective steps to change the course of the disease. The Cardiac Electrophysiology Service is dedicated to treating a patient as a whole person and to delivering the highest level of comprehensive care. We integrate the efforts of various USC physicians and nurse specialists who treat heart failure. Our mission is to provide patients with treatments that slow disease progression, prolong survival, and improve quality of life.

Patients at the USC Cardiac Electrophysiology Service have a team that will monitor and work with them to tailor therapies to their specific needs. Recognized leaders in the area of heart failure and arrhythmias evaluate patient conditions and consult with patient’s physicians to discuss findings and recommendations. We work closely with patients to ensure that they have a clear understanding of their treatment plan. It is very important to us that patients are comfortable with the therapies agreed upon.

The USC Cardiac Electrophysiology Service is unique in providing:

Efficient consultation and coordination with other top USC specialists in the areas of:

• Electrophysiology studies and radiofrequency catheter ablation
• Implantable cardioverter defibrillator (ICD) and cardiac resynchronization device (CRT) implantation and follow-up
• Investigational ablation and device therapies
• Individualized medical therapy
• Risk assessment
• Novel surgical procedures
• Alternative / adjunctive therapies

Program components composed of:

• Outpatient Arrhythmia Center
• Inpatient Electrophysiology Service
• Non-invasive comprehensive and diagnostic testing assessment
• Cardiothoracic surgery service
• Informational and interactive website