Patient-Prosthesis Mismatch Can Result in Poorer Aortic Valve Replacement Outcomes



Mr. Susman is a freelance medical writer based in Florida, USA. He travels worldwide to report from medical conferences, writing regularly for wire services, internet websites, and medical journals such as the Journal of the National Cancer Institute and AIDS.

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HOUSTON, Texas – Occurrence of patient-prosthesis mismatch in surgical aortic valve replacement procedures appears to impact survival and long-term complications, researchers reported here at the 53rd annual meeting of the Society of Thoracic Surgeons.

In one study, John Fallon, MD, instructor in surgery at the Geisel School of Medicine at Dartmouth University, Hanover, New Hampshire, reported that in cases of severe mismatch the 10-year adjusted overall survival was 35 percent compared to a 10-year adjusted overall survival of 46 percent among patients where there was no patient-prosthesis mismatch (P<o.ooo1).

And in a second study presented at the meeting, G. Michael Deeb, MD, professor of surgery at the University of Michigan, Ann Arbor, determined that mortality was doubled over two years when severe mismatch patients were compared with patients who had no mismatch. Patients with no mismatch had 17.1 percent all cause mortality at 24 months compared with 35 percent mortality at 24 months among patients with severe mismatch (P=0.02).

Dr. Deeb also determined that “Patients with small and medium annular size should be strongly considered for transcatheter aortic valve replacement (TAVR). Annular size has a significant effect on hemodynamics and the incidence of patient-prosthesis mismatch in surgical subjects, not observed in TAVR subjects.”

Patient-prosthesis mismatch occurs when the effective orifice area of the inserted prosthetic valve is too small in relation to body size. Such a mismatch generates higher than expected gradients through normally functioning prosthetic valves, and that can lead to symptoms, need for re-operation and reduced life expectancy, said Howard Song, MD, chief of cardiothoracic surgery at Ohio State University. Song was the moderator of one of the late-breaker sessions at which Deeb’s work was presented.

In his study, Dr. Fallon accessed data from the Society of Thoracic Surgeons Adult Cardiac Surgery Database, identifying 59,779 patients who were 65 years of age or older who had undergone isolated surgical aortic valve replacement between 2004 and 2014. These patients were linked to Medicare claims data.

In the study, patients judged to have no mismatch accounted for 21,053 of the cohort; 32,243 patients fit the moderate criteria and 6,483 patients were judged to have had severe mismatch. The severe mismatch patients were about 75 years of age; the patients in the other groups were about 77 years of age, a significant difference (P<0.0001).

About 48.5 percent of the patients in the study were women. The average body mass index was 28.4 kg/m2, with significant differences between the groups. Those with no mismatch had a body mass index of 26.7 kg/m2 compared with a body mass index of 32.7 kg/m2 in those with severe mismatch.

Dr. Fallon said that there was a significant eight percent increase in mortality when the moderate group was compared to the group with no mismatch; there was a 32 percent increased risk of mortality when the severe group was compared with the group with no mismatch, and there was a 22 percent increased risk of mortality when the moderate group was compared with the severe group.

Readmission rates were followed a similar pattern, with a rate of 17 percent over 10 years for patients with no mismatch versus 22 percent of the patients with severe mismatch (P<0.0001), he said in his oral session. The rate for a re-do aortic valve replacement were low but also depended on extent of mismatch. About three percent of those with severe mismatch required a new valve compared with 1.2 percent of those with no mismatch (P<0.001).

Dr. Fallon noted that his research indicates that the rate of mismatch has been declining over the last decade.

In his study, Dr. Deeb scrutinized various relationships between the size of the prosthesis, the size of the aortic annulus and whether the patients underwent surgical replacement procedures or TAVR. There were 389 patients in the TAVR group and 347 patients in the surgical group.

When comparing the two methods of implanting the devices, he observed no difference in mortality for patients with large annuli – a 26.2 percent mortality among the 115 patients treated with TAVR compared with a 26.6 percent mortality among the 96 patients who underwent surgical replacement (P=0.99). There was a numerical advantage to using TAVR in the patients with small annuli – 22.6 percent mortality among the 104 patients treated with TAVR and a 25.2 percent mortality among the 74 patients treated with surgery (P=0.70). But in the moderate group, there was an 18.3 percent mortality among the 170 TAVR patients compared with a 29.9 percent mortality among the 177 patients undergoing surgical replacement.

In discussing the trials, moderator Song said, “For patients with a small aortic valve annulus, Dr. Deeb’s study suggests that the patients have better valve function after undergoing a TAVR as opposed to a surgical aortic valve replacement. This will help to inform clinical decision making.

“It won’t just put people into a bucket, but it is another factor that helps us add to the clinical scenario along with the patients’ age, how active they are, what kind of surgical candidate they are.”

Song said that mismatch can occur even when the devices fit perfectly – they still can act differently in the body which can impact their function. “You can’t determine how the device with function in an individual until after the implant is completed,” he said. “A mismatch doesn’t mean you will have complications down the road, but it does increase the risk that complications will occur.”

Robotic sympathectomy for hyperhidrosis

Patients who suffer the embarrassing condition of hyperhidrosis – excessive sweating—can get relief with a staged robot-assisted surgical approach that appears to avoid compensatory hyperhidrosis. Compensatory hyperhidrosis occurs when sweating in the palms goes away but excessive sweating begins in other areas such as the face.

In another study at the meeting, Farid Gharagozloo, MD, medical director of thoracic surgery at Florida Hospital Celebration Health, Celebration, Florida, described outcomes among 47 patients. After a mean follow-up of 28 months, none of the patients developed compensatory hyperhidrosis following staged bilateral robotic selective dorsal sympathectomy, reported

“Robotic thoracoscopic sympathectomy for the second, third and fourth intercostal nerves with the preservation of the sympathetic chain is effective, feasible, safe and associated with the lowest reported rate of compensatory hyperhidrosis,” Dr. Gharagozloo reported.

He noted that in the medical literature the lowest reported rate of compensatory hyperhidrosis is 7.2 percent, with some researchers reporting a compensatory rate as high as 80 percent of patients.

Although, the procedure is often performed on both sides of the chest at the same time, Gharagozloo staged his patients to have the surgery performed in the patient’s dominant side first, and then the subject is brought back four weeks later for the second operation on the contralateral side.

Patient-Prosthesis Mismatch Can Result in Poorer Aortic Valve Replacement Outcomes 2The researchers scrutinized results of the case series performed from November 2011 through May 2016. The 42 patients included 22 men and 25 women with a mean age of 32 years. The mean operation time was 67 minutes; median hospitalization was three days.

Gharagozloo reported that transient compensatory hyperhidrosis occurred in 19 patients, but that condition resolved prior to the second operation. “Sustained relief of hyperhidrosis was 100 percent,” he reported. None of the patients exhibited compensatory hyperhidrosis following the second treatment.

“Hyperhidrosis can be a terrible condition for many people, it can be very embarrassing,” said Robbin Cohen, MD, associate professor of surgery at the Keck Medical Center at the University of Southern California, Los Angeles.

“This procedures by the group in Florida appears to be one method of correcting hyperhidrosis without developing compensatory hyperhidrosis,” he said.

Dr. Cohen said that most of the time patients seeks treatment for excessive sweating due to its manifestation in the palms which become sweat to the touch and can lead to avoidance of social activities. “The problem is exacerbated because the individuals are nervous about having sweaty palms and that intensifies the problem,” he said.

“This is a very common problem in the population,” he said. “There are entire clinics in California exclusively devoted to treating patients with hyperhidrosis. There are many surgeons who just do this procedure.”

He said that many clinicians and patients prefer to have the procedure done bilaterally at the same time. He said there are multiple types of techniques that have been employed in the treatment. “Some people clip the nerves,” he said. “Some people cauterize them. Some people take them out. And then you turn the patients over to the other side and do the same thing.

“The advantage of the robot is that you can just see the nerves so well and gives you the ability to know exactly where you are,” Cohen said. “This is a very thoughtful approach.”

March 2017 Health and Lifestyle

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