Electrophysiology is the study of electrical activity within cardiac tissue. Electrophysiologists are cardiologist who specialize in the diagnosis and treatment of complex irregular electrical impulses (Arrhythmias) within the heart. The Division of Cardiovascular Medicine at USC offers a unique Electrophysiology program led by internationally renowned physicians who provide unparalleled care in state-of- the art facilities.

Arrhythmias

Arrythmias are abnormal heart rhythms which may disrupt the normal, regular contractions of the heart. Normal cardiac electrical impulses originate in the Sino-Atrial node (SA) node found in the right atrium and travel down specialized cells to the atrioventricular (AV) node at the junction of the upper and lower chambers of the heart and then down to the ventricles. Normal conduction of these impulses leads to activation or depolarization of the atria resulting in contraction of the upper chambers. As the electrical stimuli travels through the AV node and into the ventricles the lower chambers are depolarized and subsequently contract. The syncrones contraction of the atria and ventricles leads to the efficient propulsion of blood throughout the chambers of the heart and the rest of the cardiovascular system.

When electrical impulses are originate and are conducted through cardiac tissue appropriately at a proper rate the heart is said to be beating in Sinus Rhythm. However, when the conduction of electrical impulses is disrupted and the regular flow of impulses does not occur, an abnormal rhythm results, an Arrhythmia.

Arrhythmias may arise from any part of the of the heart's conduction system, and are seen in both patients who have abnormal cardiac structure or function as well as in individuals with seemingly normal hearts. . Arrythmogenic rhythms may result in abnormally slow or fast heart rates. There exists a number of arrhythmias from the relatively benign to those which can lead to sudden cardiac death. Therefore, If you have been diagnosed with an arrhythmia, is imperative to discuss the risks and potential consequences of such a diagnosis with your physician.

At the USC Cardiac Arrhythmia Center our focus is the diagnosis and treatment of abnormal heart rhythms (arrhythmias). Our center provides full diagnostic services and a vast array of treatment options including:

• Diagnostic electrophysiology testing

Catheter ablation of all types of arrhythmias including:

• Atrial Fibrillation
• Atrial Flutter
• Paroxysmal Supraventricular Tachycardia (PSVT)
• Premature Ventricular Contractions (PVCs)
• Ventricular Tachycardia (VT)
• Implantation, extraction and evaluation of pacemakers and Implantable Cardioverter Defibrillators (ICDs)
• Implantation, extraction, and evaluation of cardiac resynchronization therapy devices (biventricular ICDs)
• Evaluation and Treatment of Syncope
• Evaluation and Treatment of Inherited arrhythmia syndromes including Brugada Syndrome and Long QT syndrome
• Pharmacologic (Drug) Treatment of Arrhythmias in appropriate cases
• Treatment of cardiomyopathys and heart failure with implantable devices
• Evaluation and treatment of hypertrophic cardiomyopathy and prevention of sudden cardiac death

Supraventricular Arrhythmias

Supraventricular arrhythmias are abnormal rhythms which arise from cardiac tissue in the upper chambers of the heart. The term Supraventricular arrhythmias encompasses an heterogeneous group of rhythms each amenable to different diagnostic and therapeutic techniques. Below are description of some specific arrhythmias within this broad category.

Atrial Fibrillation

Center for the Comprehensive Treatment of Atrial Fibrillation Clinical Brief View/download PDF file, 1MB

Atrial fibrillation, commonly referred to as AFIB is one of the most common arrhythmias effecting approximately 2.3 million of Americans, whose prevalence increases with age.

It is caused by a breakdown in the highly coordinated transmission of electrical impulses in the atria. The failure of proper transmission of impulses results in cessation of appropriate contraction in the upper chambers, instead resulting in the atria to "quiver". This causes dyssynchrony and inefficient movement of blood from the atria to the ventricles.

AFIB can arise in any individual, even in those who do not have any underlying heart disease. People who have AFIB may experience a number of symptoms including palpitations, decreased exercise tolerance, and fatigue.

Individuals with AFIB are at risk of developing clots in their atria because if the inefficient transmission of blood from the upper to the lower chambers. Certain risk factors such as age, history of heart failure, diabetes, hypertension, and previous history of stroke have been shown to increase the incidence of clot formation in patients with AFIB. These clots may have devastating consequences if they enter the systematic circulation and may require anticoagulation therapy to prevent such adverse outcomes.

3 Dimensional View of the Pulmonary Veins on a CT Scan

Click on the animation below to learn more about Atrial Fibrillation.

(Click to view animation)

Wolff Parkinson White Syndrome

Wolff Parkinson white syndrome (WPW) is an arrhythmia which is a consequence of electrical impulses bypassing the AV node as they propagate from the atria to the ventricles. The result of direct conduction between the chambers leads to earlier excitation of the ventricles in comparison to if the impulse had been transmitted through the AV node. WPW may be seen in individuals with otherwise normal hearts as well as in patient's with congenital or structural abnormalities.

Patients with WPW may be asymptomatic, however others may experience occasional palpitations, transient loss of conciouiness and in rare cases, sudden cardiac death. WPW is usually diagnosed by an EKG and may be managed with routine medications. Nevertheless, depening on one's cardiac history, symptoms, and other risk factors further evaluation may be undertaken including performing an EP study and if indicated a radiofrequancy ablation.

Ventricular Arrythmias

Ventricles arrhythmias are abnormal rhythms which originate in the lower chambers of the heart. The spectrum of ventricular arrhythmias ranges from the relatively benign to life threatening rhythms including ventricular tachycardia (VT) and ventricular fibrillation (VF).

VT/VF may arise in a number of clinical situations including but not limited to electrolyte abnormalities, secondary to medications, structural heart disease, during or after a heart attack or with any cardiac or surgical manipulation. Symptoms may include chest pain, palpitations, shortness of breath, lightheadedness, weakness and may result in loss of consciousness.

The Electrophysiologists at USC have been recognized for their innovative diagnostic and treatment for ventricular arrhythmias. They offer a number of treatment options including medical therapy, radiofrequency ablations, as well as implantable devices to prevent sudden cardiac death by these potentially fatal rhythms.

Click on the Animations below to learn more about Ventricular Tachycardia and Fibrillation.

(Click to view animation)

(Click to view animation)

(Click to view animation)

Diagnosis of Arrhythmias

(Click to view larger image)

An EKG is the sentry test to provide general information about the heart's electrical activity. It often provide pertinent information about the rate, rhythm and origins of the electrical activity.

However, if more information is required a Holter monitor or an event recorder might be used to capture arrhythmias which are intermittent and can not be captured on a single EKG.

Nevertheless, if the above tests do not yield adequate or sufficiently detailed information an Electrophysiological Study (EP Study) may be performed. During an EP Study, the Electrophysiologists will provoke a patient's heart into an arrythmogenic rhythm, and measure the heart's electrical signals during this period of erratic behavior. The heart is electrically mapped, allowing the physician to determine the precise location of any electrically problematic tissue. Though the heart is provoked to function abnormally, the patient is in a controlled environment under the direct care of trained physicians and dedicated staff.

An EP Study is invasive. Patients are brought under conscious sedation for optimal comfort. A catheter - a narrow, flexible tube with electrical monitoring electrodes at the tip - is inserted into a blood vessel in the groin or the neck, and threaded through the vasculature into the patient's heart. This safe technique allows your electrophysiologist to perform an analysis of the heart's electrical activity with a high degree of accuracy and precision.

During an EP study specific areas of cardiac tissue may be identified as potential arrythmogenic sources. If such a focus is found it may be remedied by a procedure called an Ablation.

Ablation

An ablation is a minimally-invasive procedure, where during a EP study an specialized catheter is advanced to an "irritable focus" of cardiac tissue which may be instigating an arrhythmia. Once the catheter is in place, an electrophysiologist may employ short-range radio-frequency waves as well as cryotheray or infusion of alcohol to carefully destroy a small amount of the damaged tissue while not harming the surrounding cardiac architecture.

With the disrupting tissue removed, the heart's normal electrical signal will be free to propagate down a normal, healthy pathway.

Radiofrequency Ablation is a common procedure performed routinely by Electrophysiologists at USC. During the procedure, patients are placed under conscious sedation for optimal comfort. The procedure may lasts up to 8 hours, and patients are normally able to go home later the same day or the following morning.

Cardiac Devices

Cardiac Pacemakers

If it is determined that an arrhythmia is caused by a problem with the Sino-Atrial Node (SA Node) - the specialized bundle of heart tissue that initiates the heart's electrical signals - a Cardiac Pacemaker may be prescribed. A pacemaker is a small device placed under the skin of the upper chest help pace the heart at a healthy rate.

Implanted pacemakers output a regular, low-energy electrical pulse to correct faulty signaling in the SA Node. They are able to slow or accelerate the beating of the heart, and are able in some cases to coordinate the electrical signaling between different chambers. Cardiac pacemakers are highly sophisticated devices; they are able to monitor a patient's temperature, respiratory rate, and other cues and adjust the heart rate in relation to changing metabolic activity and other bodily conditions. All cardiac pacemakers implanted by USC physicians also function as remote monitoring devices. The devices are able to monitor the patient's heart condition and device status, and securely transmit this information on-demand through a phone line to the USC Cardiovascular team. This networked monitoring capability gives USC Cardiovascular professionals a much more comprehensive picture of their patients' disease condition, allows patients to travel more and make fewer appointments, and improves communication and overall quality of care.

The implantation of a cardiac pacemaker is a minimally invasive, routine procedure lasting an average of one hour. The patient is anesthetized, and the device is implanted through a small incision in the chest. The patient is normally able to go home the morning following the procedure after it is determined that the device is functioning properly. Current cardiac pacemakers possess a battery life of up to 15 years.

(Click to view animation)

Implantible Cardioverter Defibrillators (ICD)

If a patient's heart is found to be at risk or has previously experienced certain types of life-threatening arrhythmias, an ICD device may be recommended by your cardiologist. Without an implanted ICD, slipping into a deadly ventricular arrhythmia can cause sudden cardiac arrest, immediate loss of consciousness, and death within minutes if untreated. The ICD is very similar to a cardiac pacemaker in size. However, its function is to continuously monitor the heart's rhythmic activity and to automatically defibrillate it when an unsafe rhythm is detected. A defibrillation is the delivery of an electrical shock to the cardiac tissue to restore regular rhythm and function. Like all other device implanted at USC, all ICDs posses the capability to remotely transmit networked physiological and device information remotely to USC medical thus allowing more accurate and efficient coordination of care.

An Xray of an Implanted ICD

(Click to view animation)

Implantation of an ICD is very similar to that of a cardiac pacemaker. The procedure lasts an average of one hour, is minimally invasive through a small incision in the chest, and the patient is normally able to go home the morning following the procedure. Current ICD devices possess battery life of up to 8 years.

(Click to view animation)

Cardiac Resynchronization Therapy Devices (CRT)

A CRT device is a multifaceted tool which is implanted in a similar fashion to a pacemaker and ICD. Similar to other devices a CRT is implanted subcutaneously in the upper chest and wires from the device are attached to different chambers of the heart.

However, CRT devices function to electrically coordinate the rhythmic contractions of the upper and lower chambers of the heart. Some CRT devices are also equipped with a defibrillator, allowing these devices not only to coordinate carried contraction but also function as an ICD when a patient experiences a life threatening arrhythmia.

The purpose of the resynchronization therapy is to increase the hemodynamic capabilities of a damaged or diseased heart. CRT devices have been shown to have a tremendous benefit in patients with heart failure. The improved coordinated function caused by a CRT device in heart failure, promotes more efficient delivery of blood throughout the body and thus improved symptomology and enhanced exercise capacity.

A Diseased Heart Pre CRT Implantation

A Diseased Heart Post CRT Implantation

Like all other devices implanted at USC, CRT's carry the capacity to be linked to the cardiovascular network, transmitting real time data and remote progress reports about the device's status and function.

The Heart Failure Program

Heart failure is a disease that affects over 2 million Americans (Heart Rhythm Society). It is a disease in which the heart is unable to adequately perfuse the body's tissues with oxygenated blood. There are a number of disease processes which may lead one to develop heart failure. When the heart begins to fail an individual may experience shortness of breath, decreased exercise tolerance, lower extremity swelling, and the need to sleep with multiple pillows. In addition to the previously stated symptoms, patients with heart failure are at increased risk of developing fatal arrhythmias due to the abnormal architecture of their heart. Patients who have severely depressed cardiac function and have had their heart failure optimized medically, have been shown to benefit from the implementation of certain devices. ICDs have been shown to decrease mortality by preventing fatal arrhythmias in heart failure patients who meet certain, specific criteria. While CRT-D provide the benefits of an ICD as well as improving cardiac function and efficiency.

A Normally functioning Heart

A Heart of a patient with Heart failure

The division of Cardiovascular medicine at USC and its cardiologists have been recognized as forerunners in the field for their incorporation cutting edge technology to standard therapies in heart failure.

Hypertrophic Cardiomyopathy

Hypertrophic cardiomyopathy is usually a genetically linked condition in which the cardiac tissue of either of the heart's ventricles abnormally hypertrophies or enlarges inappropriately. The abnormally thickened lower chamber does not "relax" properly, leading to inefficiently poor filling during diastole. In addition, the walls of the chamber may enlarge to the point in which the ejection of blood into the systemic circulation is hindered. The distorted architecture also may lead to valvular abnormalities, causing inappropriate flow through them during certain periods of the cardiac cycle.

Unlike other cardiomypathys, HCM is primarily a disease of the young, usually presenting clinically in individuals during childhood or early adolescence. Per the American Heart Association approximately 500,000 people are affected by the disease in the United States. And it is estimated that 50-60% of patients with the disease have a relative who has similar cardiac architecture.

Individuals with HCM may be asymptomatic, while others may present with shortness of breath, easy fatigability, decreased exercise tolerance, transient loss of consciousness, and palpitations. Given the aberrant profile of their ventricles, individuals are at increased risk of experiencing fatal arrhythmias. In fact, HCM is the leading cause of sudden cardiac death in young athletes. Therefore, those diagnosed with the condition should refrain from physically demanding activities.

The diagnosis of HCM is usually confirmed by obtaining an echocardiogram. Once the diagnosis is confirmed treatment options include medical management, surgical intervention, and device implantation to prevent sudden death.

The Chambers of a Normal Heart

The Chambers of a Patient with Hypertrophic Cardiomyopathy

The Department of Cardiovascular medicine in conjunction with the physicians of the CVTI offers a unique team of pediatric cardiologists, electrophysiologists, and cardiothoracic surgeons who are specialized in the treatment of HCM and are able to provide unequaled comprehensive care in one institutional setting.

Congenital Heart Disease

Individuals diagnosed with congenital heart disease posses abnormal cardiac architecture. The altered physiology of their heart and in turn their electrical conduction system even if previously surgically repaired, predisposes them to a higher rate of arrhythmias in comparison to normal individuals. This unique subset of patients require individualized care given their anatomy. The Arrhythmia Center offers thorough comprehensive care including device implementation and ablation in treatment of these complex cases.

Depiction of an Abnormal Conduction Circuit producing an Arrhythmia
in a Patient with a Surgically Repaired Congenital Defect.