Improving the safety and efficacy of robotically assisted mitral valve surgery

STUDY RESULTS

It is important to remember that with femoral artery perfusion, the blood flow is opposite to the normal direction; thus, it goes up the aorta into the head vessels, which presents its own risks and challenges. Also, during retrograde perfusion, there is a risk of dislodging atherosclerotic plaque leading to brain embolus and stroke.

Nevertheless, outcomes data showed that these procedures were safe, with just 1 death in the 1,000 cases (Table 2). There was an overall 1.4% stroke rate, with a 0.8% permanent stroke rate. Atrial fibrillation occurred in 18.9%, approximately 12% required a transfusion, and 2.5% needed re-exploration for bleeding.

In these 1,000 cases, 997 were planned mitral valve repairs, 2 were mitral valve replacements, and 1 was resection of a mitral valve fibroelastoma. Results for the mitral valve repairs were excellent, with postoperative mitral regurgitation occurring in less than 1% of patients.

There were 20 conversions to sternotomy, mainly during the earlier stages of this study. Table 3 lists the causes of conversions. Most were from residual mitral valve regurgitation, bleeding, or exposure difficulties.

PROCEDURAL IMPROVEMENTS

A primary point of interest was to identify procedural improvements that occurred during the course of the study. The areas evaluated in robotically assisted mitral valve surgery were the efficacy of the procedure in time, transfusion rates, stroke risk, how many mitral valve replacements occurred, and how many required conversion to sternotomy. These were assessed to determine whether surgical experience resulted in improvement.

Results showed that those efficiencies improved during the study. Cardiopulmonary bypass time decreased from about 140 minutes to 130 minutes. Cross-clamp time improved more dramatically from about 110 minutes to 90 minutes. And the percentage of cases requiring postoperative or intraoperative blood transfusion improved from about 24% to 10%.

PATIENT SELECTION CRITERIA: ALGORITHM

After 500 cases, enough data had been collected to create an algorithm for determining which patients would be eligible for mitral valve repair via the robotic approach vs a sternotomy-based approach. Use of the algorithm (Figure 1) relies on results from echocardiography and computed tomography (CT) for most of the selection process. Echocardiography results that indicate a sternal approach would be preferred include significant aortic insufficiency, which complicates cardioplegia delivery, severe mitral annulus calcification, left ventricular dysfunction, and pulmonary hypertension. CT results are important in assessing patients for aortoiliac atherosclerosis, femoral artery diameter, and pectus excavatum. The existence of any of these indicates a patient more appropriate for the sternal approach than the robotic approach.

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Figure 1

Algorithm for determining patient eligibility for the robotic approach to mitral valve repair.¹

ALGORITHM IMPACT

What was the effect of this algorithm? In the 500 cases after its implementation, the stroke rate decreased by more than half—from 10 incidents before to 4 incidents after—and mitral replacements dropped from 4 to 0. The rate of conversion from robotic repair to conventional sternotomy in this patient series also improved, although this likely reflects surgical experience more than the algorithm. The conversion rate initially increased as surgeons gained experience with the robotic techniques. It rose to 4% during the first 300 to 400 cases, then dropped to 2% at the 500-case mark. It leveled off for the next 300 cases before dropping to 0 toward the end of the series.

Other metrics improved as well, which were attributed to a combination of surgical experience with robotic assistance and use of the patient-selection algorithm. The stroke risk declined to 0.8%, ischemic and cardiopulmonary bypass times declined, and the transfusion rate declined. No mitral replacements were done in the last 500 cases, and the conversion to conventional sternotomy rate declined to 1%.

In conclusion, this Cleveland Clinic study showed that a combination of a focused preoperative assessment using the patient-selection algorithm and increased surgical experience with robotic techniques enhanced clinical outcomes and improved procedural efficiency associated with robotically assisted mitral valve surgery.