In 1998 scientists in France made a discovery about the underlying physiology of AF that opened the door to simpler, ultimately less invasive procedures. The French team demonstrated that the major triggers for AF’s erratic pulses don’t originate from within the heart muscle, but rather, for reasons still unknown, from the pulmonary veins entering the back of the heart. Electrically isolating those triggers in the pulmonary veins—a procedure called pulmonary vein isolation, or PVI—effectively stops many forms of AF.
Because the pulmonary veins could be reached by catheters passed through peripheral veins, that discovery potentially eliminated the need to open up the chest to operate on the heart. In addition to percutaneous approaches, minimally invasive surgical procedures have been developed to create the maze lesions. Since 2003, several surgeons, including Randall Wolf at the University of Cincinnati and Michael Argenziano at the New York-Presbyterian Hospital/Columbia University Medical Center, have collectively performed more than 1,000 such procedures, in which they get at the heart through small incisions between the ribs (on each side of the chest) and isolate the pulmonary veins while the heart continues to beat.
But PVI can also be done even less invasively from inside the heart, approached via a percutaneous catheter. These so-called catheter ablations are handled by electrophysiologists such as Jeremy Ruskin, director of the Cardiac Arrhythmia Service at the Massachusetts General Hospital (MGH), who supervised Colicchio’s treatment in 2003. According to Ruskin, the field has grown markedly since then, and 10,000 to 12,000 patients now get catheter ablation PVI procedures each year.
In a recent PVI in the MGH’s electrophysiology lab, a patient lay under conscious sedation with a tangle of catheters inside her heart. One catheter, equipped with an ultrasound camera, provided an image of the heart’s interior and blood vessels. Another mapped the junction where the pulmonary veins entered the left atrium so that physician Vivek Reddy could maneuver the long, flexible ablation catheter to precisely the right points. On a monitor, those points appeared as wide ellipses of dots superimposed around each of the four pulmonary veins on a 3-D image of the patient’s heart.
Reddy asked the engineers in the control room to rotate the map to locate an ablation site and to “slice” the image open so he could examine the ridges and funnels where the pulmonary veins enter the heart. He would use that information to avoid any injury to the veins or the esophagus, which lies directly behind the heart’s left atrium.
Reddy guided the ablation catheter, cooled by saline flowing through the small electrode at its tip, toward one of the dots and delivered a burst of radiofrequency energy to ablate that site. After the team checked to make sure the electrical signals coming from there had been adequately reduced or eliminated, it was on to the next dot, and the next. This had to be repeated at all of the ablation sites for each of the four veins. The meticulous process, with nary a dramatic moment, went on for hours. (A new device using a balloon catheter promises to isolate an entire vein with just a few applications. It’s being tested in trials at the MGH and other medical centers.)
Catheter ablations appear to be slightly less effective than minimally invasive PVI surgery, and PVI surgery as a whole seems to be 10% to 20% less efficient than the open maze. But the PVI approaches enable many more patients to get help when drugs don’t relieve AF symptoms. The recommendations of the American College of Cardiology and American Heart Association Task Force on Practice Guidelines call for patients to first try drug treatment, then catheter ablation.
The millions of older Americans with another common heart ailment, mitral valve disease, normally must work their way up a similar decision tree. The most common form of this disease is mitral valve prolapse, and about 7% of people older than 65 have moderate to severe prolapse, which may cause serious health problems. During an eight-month period, 76-year-old Ruby Lord, of Smyrna, Ga., had gone from being able to mow her lawn to needing help caring for herself, a result of the failure of her floppy mitral valve. Her overworked, inefficient heart left her vulnerable to pulmonary congestion and atrial fibrillation.
Depending on the severity of their disease, patients with mitral valve prolapse can choose from a range of treatments, both medical and surgical. Typically, one of the valve’s two leaflets has stretched and no longer snaps shut, allowing blood to regurgitate into the left atrium and back into the lungs. In most of the approximately 30,000 surgical cases each year in the United States, a section of the leaflet is cut out to tighten the valve. In Lord’s case, her doctors told her that she’d likely survive an open-heart procedure, but that she would face significant risks and a long recovery. So she opted for an experimental procedure, the percutaneous installation of a MitraClip.
The MitraClip builds on the work of Ottavio Alfieri, a cardiac surgeon in Milan who in the mid-1990s first proposed what became known as the Alfieri stitch. Alfieri suggested that instead of cutting out part of the valve, a surgeon could tack together the valve’s two leaflets so that they’re pulled tight when the valve is closed and are still able to let blood flow through “bow-tie” orifices on either side of the stitch when the valve opens. Mehmet Oz, a cardiac surgeon at Columbia University’s College of Physicians and Surgeons, who saw Alfieri present this technique at an Italian conference in 1996, later helped design the MitraClip for doing the procedure percutaneously.
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