PII: S0022-5223(95)70266-0

Abstract

We appreciate the opportunity to respond to the comments of Dr. Akins regarding our article.1de Luca L Vitale N Giannolo B et al.Mid-term follow-up after heart valve replacement with CarboMedics bileaflet prostheses.J THORAC CARDIOVASC SURG. 1993; 106: 1158-1165PubMed Google Scholar He gave us the benefit of his experience.2Akins CW Mechanical cardiac valvular prostheses.Ann Thorac Surg. 1991; 52: 161-172Abstract Full Text PDF PubMed Scopus (87) Google Scholar With regard to linearized rates of valve-related complications, data were analyzed by applying the Mantel-Haenszel test included in the program 1L of the BMDP statistical software package (BMDP Statistical Software, Inc, Los Angeles, Calif.).3BMDP Program 1L. BMDP statistical software manual. Vol 2. University of California Press, Los Angeles1990Google Scholar This test takes into account the number of events for a given time divided by the number of patients followed up for the same time interval.3BMDP Program 1L. BMDP statistical software manual. Vol 2. University of California Press, Los Angeles1990Google Scholar, 4Colton T Statistics in medicine. Little Brown, Boston1978Google Scholar In our study we assumed a 6-month interval. This type of calculation is presented in our article as the curve at the bottom of each graph. The combined and separate linearized rates presented in our report were obtained with this test, by summing up the patient-year incidences of each time interval divided by the total number of time intervals of follow-up.3BMDP Program 1L. BMDP statistical software manual. Vol 2. University of California Press, Los Angeles1990Google Scholar, 4Colton T Statistics in medicine. Little Brown, Boston1978Google Scholar Moreover, linearized rates of each subgroup of patients were calculated including only the patients undergoing that operative procedure. For all these reasons, they would be better defined as linearized incidences than as linearized rates, and we apologize not to have mentioned this statistical aspect in our paper. On the other hand, linearized rates are generated by the number of events divided by the number of patient-years. As requested by Dr. Akins, we list the linearized rates of our population for the valve-related complications that we have noted for the combined and separate operative procedures (Table I). The rates were calculated according to this latter method.Table ILinearized rates of valve-related complicationsEventTotal (%/pt-yr)MVR (%/pt-yr)AVR (%/pt-yr)DVR (%/pt-yr)NSD0.6—0.52ARH1—1.52TE1.52.91—Reoperation0.61.7——PVE0.2—0.5—VRD1.51.21.52ARH, Anticoagulant-related hemorrhage; AVR, aortic valve replacement; DVR, double (mitral and aortic) valve replacement; MVR, mitral valve replacement; NSD, nonstructural dysfunction; PVE, prosthetic valve endocarditis; TE, thromboembolic events; VRD, valve-related deaths. Open table in a new tab ARH, Anticoagulant-related hemorrhage; AVR, aortic valve replacement; DVR, double (mitral and aortic) valve replacement; MVR, mitral valve replacement; NSD, nonstructural dysfunction; PVE, prosthetic valve endocarditis; TE, thromboembolic events; VRD, valve-related deaths. We are grateful to Dr. Akins for raising this statistical issue of our paper that would have been overlooked otherwise. A correct analysis of data on cardiac valvular prostheses allows a better understanding of the results of such procedures and enables surgeons to choose the appropriate prostheses for their patients.