Surgeons take aim at postoperative AFib
A new approach to the study of postoperative atrial fibrillation (AFib) could eventually lead to fewer complications and shorter hospital stays for many heart surgery patients.
Postoperative AFib, in which the heart’s upper chamber beats erratically, is the most common complication after cardiovascular surgery.
“One-third to one-half of patients who have heart surgery get postoperative AFib,” says Spencer Melby, MD, Washington University heart surgeon at Barnes-Jewish Hospital. “These patients stay in the hospital one to two days longer, their cost of care is much higher, and they have higher rates of stroke and mortality than patients without postoperative AFib.”
Melby is performing T1 translational research to explain the underlying causes of postoperative AFib. He is the first to focus on inflammation within the pericardium — the fluid-filled sac surrounding the heart. His work involves patients undergoing cardiovascular surgeries; he has found that their pericardial fluid, routinely drained during surgery, contains higher levels of inflammatory substances than did their blood. The findings point to inflammation around the heart as a likely contributor to postoperative AFib and other surgery-related heart complications.
Reviewing patient histories, Melby and colleagues have since mapped the typical timing of postoperative AFib and associated risk factors: AFib occurs most frequently right after surgery or during a second phase about 48 hours later. The first period is likely related to trauma from surgery, but the second is almost certainly related to inflammation, Melby says.
The next step is to determine which inflammatory substances may induce atrial arrhythmias in an animal model and to study the effects of administering anti-inflammatory drugs within the pericardium, as opposed to systemically. The long-term goal is to identify potential drugs to prevent postoperative AFib and test them in human clinical trials.
Over the past 30 years, treatment of postoperative AFib has improved, but its rate of occurrence has not changed, Melby says.
“There is not going to be any one factor that cures postoperative atrial fibrillation,” he says. “There are too many risks and contributing pathologies. At Barnes-Jewish, we perform 1,200 heart surgeries a year, so 400 to 500 people a year have postoperative atrial fibrillation. Any decrease in that rate would be meaningful.”
Basic science fosters surgical solutions
Translational research in atrial fibrillation (AFib) at Washington University bridges the gap from bench to bedside and has been funded by the NIH for 30 years.
AFib affects more than 2 million Americans and can lead to cardiomyopathy, heart failure and stroke. In 1987, Washington University physician-scientists’ important findings on electrophysiology of the heart led to development of the Cox-Maze procedure by surgeon James Cox, MD. It became the gold standard for surgical treatment of AFib. In the operation, surgeons made small incisions in the heart, creating a “maze” of scar tissue to guide errant electrical signals in the heart back to more normal pathways.
Since then, Cardiothoracic Surgery Chief Ralph Damiano Jr., MD, the Evarts A. Graham Professor of Surgery, has developed new versions of the procedure that make it easier to perform — replacing incisions with radiofrequency ablation and adapting the procedure to minimally invasive techniques.
Highlights
- In the past 10 years, cardiac surgical procedures in the Section of Cardiac Surgery have grown from almost 1,400 to 2,200 per year — an increase of about 60 percent. Part of the growth is attributed to outreach programs in Mount Vernon and Quincy, Illinois, which improve care in those regions and create a referral system for more complex surgeries at Barnes-Jewish Hospital. The number of valve cases and implantations of ventricular assist devices also have risen sharply.
- The division established a cardiac surgery service at the John Cochran VA Medical Center. Steve Guyton, MD, MHA, who came from Oregon Health & Science University in Portland, is chief of cardiac surgery. He is joined by surgeons Spencer Melby, MD, and Michael Crittenden, MD. The service provides critical services for veterans from World War II through current-day conflicts and is the first new cardiac surgery program at a VA hospital in more than a decade.
- In the past 10 years, 21 of 33 graduates of the Thoracic Surgery Residency Program have gone on to academic practice. Over that period, six residents have joined the Washington University faculty. Cardiac Surgery Chief Marc Moon, MD, the John M. Shoenberg Chair in Cardiovascular Disease, is the residency program director.