Medical Device Daily Associate

The St. Jude Medical (SJM; St. Paul, Minnesota) mechanical heart valve has proven to be an effective and durable valve with low complication rates, according to a 25-year retrospective study published in the March issue of the Annals of Thoracic Surgery.

The study, conducted by Cardiac Surgical Associates (also St. Paul), is one of the longest, largest and most comprehensive studies on a bileaflet prosthetic heart valve ever undertaken, St. Jude noted.

The study analyzed 4,480 patients from October 1977 – when the first St. Jude Medical valve was implanted at the University of Minnesota (Minneapolis) by Demetre Nicoloff, MD – to October 2002, marking the 25th anniversary of that milestone.

The study's primary objectives were to document patient survival and valve-related events or complications during the 25-year period.

An independent database was created to study patients who had received one of the company's aortic valve replacements (AVR) or mitral valve replacements (MVR) during this timeframe. To ensure accuracy, clinical study documents from prior studies were crosschecked with the new data. These efforts resulted in an astonishing 95% complete follow-up covering 32,190 patient years.

In total, there were 2,982 AVRs and 1,498 MVRs and concomitant coronary artery bypass grafting was performed on 42% and 33% respectively.

The paper's conclusion states: "In summary, this extensive experience demonstrates excellent function of the SJM valve in the mitral or aortic position. Valve-related events were low, most commonly caused by patient-related factors as opposed to the presence of a prosthetic valve. Valve-related mortality was low, and there have been no reoperations as a result of valve wear. The SJM valve can be recommended to patients as a prosthesis that will last their lifetime."

Operative mortality was 4% with AVR and 9% with MVR, and during the study period, overall patient freedom from late mortality was 61%. Additionally, freedom from valve-related mortality was 92%. Freedom from thromboembolic events was 85%, from bleeding events, 81%, from endocarditis, 98%, and from valve thrombosis, 99%. There was one reported MVR structural failure and no reported failures for the AVR.

The total reoperation rate for reasons other than structural valve failure was only 1.9% for the entire study population.

"This exhaustive, in-depth study represents the most complete retrospective evaluation of a bileaflet prosthetic valve ever conducted," said Robert Emery, MD, the study's lead author at Cardiac Surgical Associates in a statement. "The process involved multiple steps and crosschecks to ensure the completeness and accuracy of all data. These results validate the long-term effectiveness and safety of the St. Jude Medical mechanical heart valve, which is designed to last over a patient's lifetime."

St. Jude spokesperson Peter Gove emphasized for Medical Device Daily the importance of the large number of participants and the length of time involved in the study. It has, he said, "followed a large number of patients for a large amount of time and that's important."

Emery and his colleagues said the fact that inherent thrombogenicity of the prosthesis and the resultant need for anticoagulation remain the major causes of valve-related events in the patients study population. They noted that at 15 years, the cumulative incidences of thromboembolic and hemorrhagic events reach 15% and 21% respectively with AVRs and 20% and 20% respectively with MVRs.

"These values are important, as nearly 50% of patients are still alive at 15 years," the studies' authors wrote.

More importantly, the study noted that there were 61 fatal thromboembolic events after AVR (14% of all thromboembolic events after AVR). Similarly, 15% of thromboembolic events after MVR were fatal (42 of 293) as were 11% of hemorrhagic events after AVR (63 of 589), and 7% of hemorrhagic events after MVR (21 of 285).

The authors said that "excellent hemodynamic performance" was the initial benefit of the SJM valve, compared with other clinically available mechanical valve prostheses. There were, however, hemodynamic gradients with the company's smaller size systems (19 mm, 20 mm).

This, they noted, led to the change in the sewing ring configuration (SJM HP) and ultimately to the valve housing itself (SJM Regent), "further improving hemodynamics and becoming the first mechanical valve to demonstrate improved left ventricular mass regression."

The company has been a world leader in mechanical heart valve technology since its founding in 1976. In November 2004, the company reported its 1.5 millionth mechanical valve implant in Iwate, Japan – the only heart valve company to achieve this milestone, it said.

"We would like to thank Dr. Emery and his colleagues for undertaking this thorough analysis of the St. Jude Medical mechanical heart valve," said George Fazio, president of St. Jude Medical's Cardiac Surgery Division. "More than 1.5 million patients around the world have benefited from the quality and durability of the St. Jude Medical mechanical heart valve."