No Need for Robotics?

Minimally invasive procedures, which reduce scarring and pain, improve patient recovery and save costs, are increasingly replacing open surgery. However, argues Dr. Robert Bonow, when it comes to heart valve procedures, minimally invasive does not automatically mean better.

Valvular heart disease is responsible for nearly 20,000 deaths each year in the US, and contributes to almost 42,000 deaths. Echocardiography is commonly used to diagnose valve problems and continues to evolve in important ways. “In addition to two-dimensional imaging of the heart, we can also perform Doppler echocardiography, which allows one to look at the blood flow through the heart, and then calculate the severity of how diseased the valve might be, whether it’s too tight or too leaky, and quantitate that severity,” says Dr. Robert Bonow, Chief of Cardiology at Northwestern Memorial Hospital. “The echo also allows the clinician to assess the effect of the valve disease on the rest of the heart,” he adds.

Other tests, like magnetic resonance imaging (MRI) and computed tomography (CT), play a role in further evaluating the heart in those patients where the heart echocardiogram is providing conflicting information.

“One thing that MRI does exclusively well, which is an advantage over echo, is in assessing some of the extracardiac structures. In particular, many patients with disease of the aortic valve also have disease of the aorta itself. And many times, it’s the aortic disease which is actually more of a clinical problem for the patient than the actual valve disease,” Bonow states. “However,” he points out, “MRI many times just replicates what the echocardiogram can do.”

Treatment
Once diagnosed, treatment can follow. Yet although minimally invasive surgery has revolutionized many surgical procedures over the last few years, heart valve procedures remain open heart surgery, requiring a cardiopulmonary bypass.

“Minimally invasive is relative,” Bonow remarks. “Usually, what it means is a smaller incision. Now, many surgeons are not doing, for example, a full sternotomy but only a mini-sternotomy, which involves only half the sternum.”

Other techniques, especially for the mitral valve, come in from the side through the right ribcage. “That’s the way robotic surgery is performed now. And there are some minimally invasive valve repair procedures that are possible that way, or even valve replacement. But the patient still has to go on cardiopulmonary bypass,” Bonow adds.

Patients, Bonow continues to say, tend to prefer a minimally invasive procedure, either because they have to spend less time in the hospital, because they think it hurts less or is less of a cosmetic issue afterwards. “What we have to explain to the patients is the finding that there’s much more pain involved coming from the side, because you’re cutting through the intercostal muscles between the ribs, as opposed to going through the sternum. It also takes longer to get the patient on a cardiopulmonary bypass because you’re going through smaller windows, and you’re trying to do this with limited exposure of the heart. Doing this with a robot, in particular with external control systems, may take longer. “

Finally, Bonow relates, the results of a robotic valve procedure may not actually be that good. “If you’re doing a mitral valve repair, you’re more likely to have residual mitral regurgitation after a minimally invasive procedure than you are with a very highly trained surgeon who can do the usual valve repair through a standard sternotomy.”

Minimally invasive doesn’t automatic mean better, Bonow concludes. “If you are a very good surgeon at repairing valves using the standard procedures, which continue to evolve through advances in valve ring technology, there’s no need to do robotics,” he states, adding: “I don’t want to minimize the fact that the leaders in the robotic surgery field are very good and skilled surgeons who can do the standard operation very well. But what sounds like it would be an easy transition – let’s move into robotics now; any surgeon can do this – is not quite the case.”

Skills and experience
Right now, and for the near future, Bonow is certain that the surgical advances that are going be most important will be the ones using standard open heart procedures. “We need to make sure that we don’t go too far down the pike with these newer procedures without looking at the big picture. The big picture is that many patients who need heart valve surgery are not getting it. Many patients who are getting it do so in centers which do very few operations,” he says.

The average cardiac surgeon in the US does 12 valve operations a year. “Clearly,” Bonow emphasizes, “you need to be doing 50 or 75 or more to be really skilled at this. And it’s true for hospital volumes as well. It’s been shown that for mitral valve replacement in the Medicare population over 65, in a low volume centre the mortality is 20 percent, whereas in a higher volume centre it’s under 10 percent. There certainly is a movement within the professional societies to improve quality across the board, and to make sure patients have the best outcome. In some cases, that may mean looking at numbers of procedures being performed by surgeons and by hospitals.”

This is especially true for new treatment methods that have been and will be replacing traditional procedures. Percutaneous stent implantation across the valve is one example, which may be replacing percutaneous balloon procedures. “This is now being done in phase II trials in Europe and Canada. It’s not started yet in the US. There is lots of excitement about this, because this is a disease essentially of old age,” says Bonow.

With old age also come comorbidities: renal failure, lung disease, coronary disease, previous strokes, to name a few, which increase the risk of aortic valve surgery. “In some patients, the predicted mortality risk of performing aortic valve replacement surgery is between 20 to 40 percent; so there’s great excitement that if we had a percutaneous mechanism of replacing the valves, it might be the best way to treat these patients.”

Making progress
Before patients can be treated, however, they need to be diagnosed – and clinically recognized. The problem, says Bonow, is that asymptomatic patients with valve disease, which should be candidates for surgery especially if cardiac dysfunction may be a result, often aren’t recognized.

“Symptomatic patients, especially if they are of older age, are being denied surgery too, even though they appear to be good candidates. In those cases, the physician feels that they’re too old and too frail, even though the results in many of those patients are quite good. That’s what’s standing in the way of making better progress at treating valvular heart disease.”

Good clinical trials, Bonow adds, showing that newer percutaneous devices are safe and effective are also needed to improve outcomes. “Within five years, we’re going to have data from multi-center clinical trials to tell us how good these devices are, and maybe identify which patients are the best candidates for them.”

Most importantly, Bonow concludes, he would like to see better ways of identifying centers of excellence, so the patients are referred to centers that can perform the best surgery at the lowest risk. “That means centers which put in prosthetic valves which are the best for certain patients at a certain age. Or for mitral valve, having patients referred to centers that do a large volume and high quality results with mitral valve repair.”

Dr. Robert Bonow is Chief of Cardiology at Northwestern Memorial Hospital and a professor of medicine at Northwestern University School of Medicine. He is a past president of the American Heart Association and has been active with the American Heart Association and the American College of Cardiology developing guidelines for valvular heart disease.