PurposeIncreasing numbers of patients with cardiac valve prostheses are being referred for magnetic resonance imaging (MRI) despite concerns about the potential for functional valve impedance due to Lenz forces. This study aims to determine, in vitro, the occurrence of Lenz forces on 9 heart valve prostheses at 1.5 T and assess the risk of impedance of valve function.Materials and MethodsA specially designed hydro-pneumatic system was used to record pressure changes across the valve indicative of any MR induced alteration in leaflet performance. Nine cardiac valve prostheses were exposed to the B-0 field at 1.5 T. Each valve was advanced through the B-0 field and continuous signals from high frequency pressure transducers were recorded and pressure drops across the valve were assessed using time correction superimposition. The delta p across the valve was assessed as a marker of any MRI induced alteration in leaflet performance.ResultsAll prostheses produced sinusoidal waveforms. Profiles were asymmetrical and there was no consistency in complex shape and valve type/sub-group. Irregularities in pressure profiles of 4 prostheses were detected indicating resistance of the occluder to the B-0 field.ConclusionThis study provides empirical evidence of the Lenz Effect on cardiac valve prostheses exposed to the MR B-0 field causing functional valve impedance and increasing the risk of valvular regurgitation and reduced cardiac output. Thus, it is essential to consider the potential for the Lenz Effect when scanning cardiac valve implant patients in order to safeguard their wellbeing. J. Magn. Reson. Imaging 2015;41:74-82. (c) 2013 Wiley Periodicals, Inc.

BACKGROUND AND AIM OF THE STUDY:Patients with mechanical heart valves require anticoagulation which is associated with significant maternal mortality (1-4%) and fetal complications (31%) in pregnancy. The study aim was to identify anticoagulant protocols and outcomes for pregnant women undergoing heart valve replacement (HVR) in the United Kingdom.METHODS:Women aged between 18 and 45 years and registered with the United Kingdom Heart Valve Registry (UKHVR) each completed a questionnaire, and their obstetric notes were reviewed. The data analyzed included valve type (mechanical, bioprosthetic, homograft), valve site (mitral, aortic, tricuspid, pulmonary), anticoagulation at confirmation of pregnancy, between 6-12 weeks and from 12 weeks to term, delivery, maternal and fetal outcomes, and cause of death. The summary statistics and a descriptive review of the findings are reported.RESULTS:Of 2,532 women eligible for the study, 922 responded. Among these women, 72 became pregnant, with 60 pregnancies in the mechanical valve (MV) group and 45 in the tissue valve (TV) group. Three anticoagulation regimes were used during early pregnancy: unfractionated heparin (UFH), low-molecular-weight heparin (LMWH) or warfarin. All women received warfarin in the second trimester and heparin for delivery. Live births were recorded in 30% of MV pregnancies and in 60% of TV pregnancies. Miscarriage rates differed markedly (37% MV versus 2% TV). Fetal outcome was poorest in the warfarin-only group, with embryopathy occurring at a dose level of 6 mg. The maternal outcomes did not differ significantly among groups. High-dose heparin during the first trimester and for delivery was effective for the majority of mechanical valves.CONCLUSION:The study results illustrate the diverse and uncertain manner in which UKHVR patients are managed during pregnancy. A national notification system would record much-needed prospective information on anticoagulation and pregnancy outcomes, thus aiding evidence-based management.

Edwards and Taylor [1Edwards M.-B. Taylor K.M. Outcomes in nonagenarians after heart valve replacement operation.Ann Thorac Surg. 2003; 75: 830-834Abstract Full Text Full Text PDF PubMed Scopus (63) Google Scholar] reported outcomes in one of the largest series of nonagenarian patients undergoing cardiac surgical intervention. They found that in 35 nonagenarians who had aortic valve replacement, there was an apparent significantly higher risk of early mortality (17%) and morbidity (77%). Outcomes evaluation in elderly patients is fundamental to our current understanding and planning of future health-care resource utilization because the current patient population is aging, and an increasing number of elderly patients are facing clinically important cardiovascular problems. It is estimated that the average 80-year-old person will live an additional 8 years and that 40% of them have symptomatic cardiovascular disease [2US Bureau of the Census, Washington, DC. Projections of the population of the United States by age, sex and race: 1983–2080. Current population report 1984Google Scholar, 3National Center for Health Statistics, 1986. National health interview survey 1983–1985Google Scholar]. However, few studies on nonagenarians exist, and most report varying outcomes, but do not critically address clear indications for cardiac interventions and their impact on quality of life rather than survival [4Samuels L.E. Sharma S. Morris R.J. et al.Cardiac surgery in nonagenarians.J Card Surg. 1996; 11: 121-127Crossref PubMed Scopus (28) Google Scholar, 5Blanche C. Matloff J.M. Denton T.A. et al.Cardiac operations in patients 90 years of age and older.Ann Thorac Surg. 1997; 63: 1685-1690Abstract Full Text Full Text PDF PubMed Scopus (29) Google Scholar]. It is common to assume in younger patients, a trade-off between a perioperative risk and a longer-term benefit often not observed for a few years [6MacDonald P. Johnstone D. Rockwood K. Coronary artery bypass surgery for elderly patients is our practice based on evidence or faith?.CMAJ. 2000; 162: 1005-1006PubMed Google Scholar]. However, this may not hold true for elderly patients in whom the perioperative risks are higher and whose chances of living long enough to experience the long term-benefits are smaller [6MacDonald P. Johnstone D. Rockwood K. Coronary artery bypass surgery for elderly patients is our practice based on evidence or faith?.CMAJ. 2000; 162: 1005-1006PubMed Google Scholar]. Edwards and Taylor did not provide detailed information on all patients in their study. They limited their analysis to only 51% (18/35) of patients. Information on all patients might have allowed one to identify trends and possibly risk factors for mortality and morbidity in nonagenarians. Despite these limitations, the 17.1% 30-day mortality rate among the 35 patients, 89% of whom underwent an elective procedure, suggests significant risks associated with cardiac surgical intervention in nonagenarians. At our center, we evaluated outcomes in a group of 10 consecutive nonagenarians who underwent a variety of cardiac surgical interventions ranging from minimally invasive direct coronary artery bypass grafting to combined aortic valve, mitral valve, and coronary artery bypass grafting procedures. Contrary to the study by Edwards and Taylor, a majority of the procedures were performed on an urgent basis with an average EuroSCORE of 11 (range, 8–14), which is predictive of a mortality rate of 25% or higher. There were no intraoperative deaths, but many patients sustained major complications resulting in a freedom from death or major morbidity of only 25% and a mortality rate of 40%. Our findings confirmed that urgency is a well-known predictor of poor outcome in elderly patients [7Akins C.W. Daggett W.M. Vlahakes G.J. et al.Cardiac operations in patients 80 years old and older.Ann Thorac Surg. 1997; 64: 606-615Abstract Full Text Full Text PDF PubMed Scopus (220) Google Scholar]. One must be careful in interpreting the results from studies evaluating outcomes in nonagenarians because all involve small, select populations. This does not mean that cardiac procedures should be withheld from nonagenarians, but it indicates that we must pay increasing attention to preoperative patient selection to improve outcomes. All efforts should be made to address this problem by a variety of approaches such as combining data from multiple centers to increase statistical power or using meta-analysis techniques to combine already available publications to identify risk factors. ReplyThe Annals of Thoracic SurgeryVol. 78Issue 2Preview Full-Text PDF

Objective: To assess the 30-day mortality, long-term survival and freedom from reoperation following surgery for prosthetic endocarditis (PVE). Method: A retrospective analysis of data from the UK Heart Valve Registry of 322 patients who had undergone single mechanical/bioprosthetic valve replacement for PVE between 1 January 1986 and 31 December 1996, The mean age was 54.9 +/- 12.8 years and 213 (66.1%) were males. There were 170 aortic and 152 mitral valve implantations. Eighty-five (26%) of the infected valves were bioprosthetic and 237 (74%) were mechanical. Of the new prostheses implanted 53 (17%) were bioprosthetic and 269 (83%) were mechanical. Of those with infected bioprostheses, 50 (15.2%) had mechanical valves at redo surgery, whilst 219 (68.3%) of infected mechanical prostheses were re-replaced by mechanical prostheses. The follow-up was 98% complete with a total of 1084.9 patient years. Results: The 30-day mortality was 63 (19.9%; 95%CI 15.9-24.7%). There were 85 late deaths. One, 5 and 10 year survival rates were 67.1% (61.6-72.0%), 55.0% (49.0-60.7%) and 37.6% (27.9-47.2%), respectively. Age was the only significant determinant of 30-day mortality (P = 0.04). Age (P = 0.001) and explanting of infected bioprosthesis and replacement by mechanical valve (P = 0.04) determined long-term survival (P = 0.001). The incidence of re-reoperation was 9.9%. Freedom from reoperation for PVE was 88.4, 87.3 and 87.3% at 1, 5 and 10 years, respectively. Explanting of bioprosthesis and replacement by mechanical valve (P < 0.001) and reoperation within 60 days of native valve replacement (P = 0.02) were determinants of reoperation for PVE. Freedom from death or reoperation was 61.1, 50.6 and 34.2% at 1, 5 and 10 years, respectively. Age (P = 0.003), explanting of bioprosthesis and replacement by mechanical valve (P = 0.002) and the period between prosthetic re-replacement (P = 0.04) determined freedom from death or reoperation. Conclusion: Operation for PVE carries a high 30-day mortality and reduced long-term survival. There is no evidence that type of prosthesis used for re-reoperation determines survival or freedom from re-reoperation. (C) 1998 Elsevier Science B.V. All rights reserved.

Background. Little is known of time-related outcome and comparative performance of biological and mechanical prostheses following tricuspid valve replacement (TVR).Methods. A retrospective UK Heart Valve Registry study (Jan 1, 1986 to June 30, 1997) identified 425 patients who underwent TVR. Two-hundred twenty-five (52.9%) received biological and 200 (47.1%) received mechanical valves. One-hundred sixty (38%), 158, and 76 had isolated, double, and triple valve replacements, respectively. The follow-up was 96% complete with a total of 1,585 patient-years.Results. Thirty-day mortality for TVR was 17.3% (73 deaths). One-, 5-, and 10-year survival rates were 72.2%, 59.9%, and 42.9%, respectively. Year of operation (p = 0.04), age (p = 0.04), and number of valves implanted (p = 0.03) predicted overall mortality. Age (p < 0.001) and year of operation (p = 0.002) predicted overall survival. Thirty-day mortality for biological and mechanical prostheses was 18.8% and 15.6%, respectively. One-, 5-, and 10-year survival rates were 70.5%, 61.5%, and 47.7% for biological and 74.0%, 57.9%, and 33.9% for mechanical prostheses, respectively. Freedom from reoperation at 1 and 10 years was 98.7% and 97.4%. Freedom from death or reoperation was 71.2% at 1 year and 41.9% at 10 years. None of the above outcomes was significantly different between the type of valve prostheses.Conclusions. TVR carries a high 30-day mortality and a poor longer term survival. No superiority could be identified for biological or mechanical prostheses in the tricuspid position for either survival or reoperation.