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Winter 2008: Heart

Arrhythmias Treated with Less Invasive Procedures

Fifty years of innovation in cardiac electrophysiology have turned this cardiology subspecialty into a leader in medical innovation, often offering curative treatments to previously intractable heart arrhythmias.

Implantable devices now not only regulate slow heartbeats (bradycardia), but can reset dangerously fast heartbeats (ventricular tachycardia) with a strong electrical shock. Ablation techniques effectively cut off faulty connections, or short circuits, in the heart’s electrical wiring and provide permanent relief from uncomfortable and sometimes dangerous heart-rhythm irregularities. Minimally invasive treatment approaches can now address electrical short circuits both inside and outside the heart, eliminating the surgical trauma of an open-heart operation and sending patients home the same day.

“Electrophysiology has emerged as one of the ‘Top Gun’ specialties within medicine,” says Kalyanam Shivkumar, M.D., Ph.D., director of the UCLA Cardiac Arrhythmia Center and Electrophysiology Programs. “Arrhythmias that were previously thought to be incurable are now being effectively managed, and sometimes cured, with catheter ablation and advanced implant technologies.”

Atrial fibrillation involves disordered electrical activity in the upper chambers of the heart, or atria. The condition initially causes brief bouts of irregular and rapid heartbeats and usually progresses to longer episodes, eventually becoming recurrent and finally chronic. Patients may experience palpitations, fatigue, shortness of breath or chest discomfort, and approximately one-sixth of all strokes are due to atrial fibrillation. Ventricular arrhythmias, those arising from the lower chambers of the heart, are particularly dangerous and increase risk of sudden death due to cardiac arrest, which causes more than 250,000 deaths in the U.S. each year.

Before the first implantable cardiac pacemaker in 1958, cardiologists had few tools beyond medication for addressing arrhythmias. Today, implantable cardioverter defibrillators (ICDs) address a range of heart-rhythm abnormalities. In addition to monitoring and correcting for slow heartbeats, some ICDs detect life-threatening ventricular tachycardia and administer a strong electric shock to reset the rate. “It’s like having an emergency response team standing by 24/7,” Dr. Shivkumar says.

Another type of ICD improves the squeezing function of the heart by resynchronizing the heart muscle of both the right and left lower chambers. And research is ongoing into implantable devices that monitor and regulate blood pressures within the heart.

Innovative research with catheters and energy sources in the late 1980s led to the first minimally invasive ablation options that used electricity, radiofrequency and eventually other energy sources to correct troublesome and dangerous arrhythmias.

Endocardial ablation, which uses heat to destroy abnormal tissue inside the heart, is the standard of care for both atrial and ventricular arrhythmias. This outpatient procedure involves threading the wires directly into the heart through the neck or groin veins. X-ray ultrasound images and sophisticated mapping systems diagram the heart’s electrical circuitry and guide catheter placement. “It allows us to get a roadmap of the abnormal heart rhythm and pinpoint the source of the arrhythmia,” Dr. Shivkumar says.

After evaluating the roadmap, physicians use the wires to apply electrical current or radiofrequency to trouble spots. “Abnormal tissues are literally burned from the circuit, patients go home the same day and, in some cases, the result is a cure for life,” Dr. Shivkumar says. About 30 percent of ventricular arrhythmias originate from tissue on the outside of the heart and cannot be treated effectively with endocardial ablation (ablation inside the heart). UCLA physicians helped perfect an alternative called epicardial ablation, and about five years ago became the first to use the procedure on the West Coast.

Epicardial ablation involves threading a wire through a catheter inserted beneath the rib cage to reach the exterior surface of the heart and destroy problem tissue with either heat or cold. As with endocardial ablation, this outpatient treatment carries low risk of complications and most patients resume normal activities within a few days.

Alternative ablation techniques using ultrasound, cryogenic and microwave technologies are also under investigation to further expand and refine ablation options. “I can envision a day when we will be able to gather the information we need and treat these patients using fully non-invasive means,” Dr. Shivkumar says. “Someday you will be able to do all this without even having to thread a wire into a patient.”

Refinements in radiology also have played a large role in advancing the capabilities of electrophysiology in addressing heart arrhythmias. High-resolution computed tomography (CT), magnetic resonance (MR) and ultrasound images have improved diagnosis, planning and treatment.

“Radiology advances have created dramatic improvements in temporal and spatial resolution,” Dr. Shivkumar says. “We can get the data quickly, and we can see a lot more of the heart. Data sets like this have greatly improved our understanding of the function of the heart.”





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