Comparative method for actuarial analysis of cardiac valve replacements

15 years experience with 615 homograft and autograft aortic valve replacements

Homograft valve replacement of the diseased aortic valve with a homologous aortic valve inserted in the sub-coronary position was first performed in July 1962 (Ross 1962). The procedure of transferring the patients autologous pulmonary valve to the aortic position has been used since 1967 (Ross 1967).

The long term performance of homograft valves has not been regarded as satisfactory in some centres (Cope-land 1977, Anderson & Hancock 1977) whereas others have shown it to be an excellent valve replacement (Barratt-Boyes, 1977, Bodnar et al 1979).

The differing experiences may be the results of alternative methods of sterilization, preservation and surgical insertion. This paper presents information on isolated aortic valve replacements with either homograft or autograft valves over a 15 year period.

Three-year outcomes following sirolimus- versus paclitaxel-eluting stent implantation in an unselected population with coronary artery disease (from the REWARDS Registry)

The Registry Experience at the Washington Hospital Center with Drug-Eluting Stents (REWARDS) study includes unselected patients with coronary artery disease treated with sirolimus-eluting stents (SESs; n = 2,392) or paclitaxel-eluting stents (PES; n = 1,119). This study aimed to examine the long-term safety profile of the 2 stents in a "real-world" population, especially in relation to stent thrombosis, and to compare differences in the diabetic cohort. Patients were followed for 3 years with regard to major adverse cardiac events (MACEs), including death, Q-wave myocardial infarction, and target lesion revascularization. Rates of stent thrombosis were also studied. Baseline characteristics were similar between stents. Although MACE rates at 3 years were similar (SES 28.1% vs PES 28.9%, p = 0.62), there was a significant difference in unadjusted rates of target lesion revascularization (SES 15.6% vs PES 12.6%, p = 0.03), death (SES 15.7% vs PES 19.0%, p = 0.02), and Q-wave myocardial infarction (SES 0.8% vs PES 2.1%, p = 0.003). After multivariable Cox regression to adjust for confounders, there was no significant difference in overall MACEs. Incidence of stent thrombosis was higher in the SES group (SES 2.2% vs PES 1.6%, p = 0.22), but this was not statistically significant (hazard ratio 1.6, 95% confidence interval 0.8 to 2.9, p = 0.17). Overall, diabetics had a higher MACE rate, but there was no difference between insulin- and noninsulin-dependent diabetics. In conclusion, at 3 years, PES and SES achieved similar results in MACEs and stent thrombosis. This should foster confidence that SES or PES can be compared to second-generation drug-eluting stents without concerns for safety or efficacy.

Competing risks after coronary bypass surgery: the influence of death on reintervention

OBJECTIVE

For groups of patients at high risk of death, such as older patients, the actual probability of experiencing a nonfatal event, such as reintervention, must be far smaller than the potential probability were there no attrition by death. Competing risks analysis quantifies the difference.

METHODS

Multivariable analyses were performed for the competing events death before reintervention, reoperation, and percutaneous transluminal coronary angioplasty in 2001 patients after bilateral internal thoracic artery grafting and in 8123 after single internal thoracic artery grafting. Follow-up was 9.7 +/- 3.0 years and 10.8 +/- 5.2 years in bilateral and single internal thoracic artery groups, respectively.

RESULTS

Patients receiving single grafts experienced shorter survival and more reinterventions (P <.0001). However, other risk factors for death included old age (P <.0001), but risk factors for reintervention included young age (P <.0001). This difference confounds interpretation of event-free survival that is clarified by competing risks analysis. Death reduced the potential benefit of bilateral internal thoracic artery grafting on reintervention by angioplasty from a median of 8.5% to 5.5% at 12 years and by reoperation from 9.3% to 6.8%, with progressively greater erosion of benefit from attrition by death as age increased. Competing risks simulation confirmed that young age was a true risk factor for reintervention, excluding the explanation that it reflected simply passive attrition by death as patients age.

CONCLUSIONS

Even after accounting for attrition by interim deaths, bilateral versus single internal thoracic artery grafting and older age are associated with fewer reinterventions. However, in high-risk patients, its benefit on freedom from reintervention is eroded considerably by death.

Surgery for Combined Rheumatic Valve and Coronary Artery Disease

Between 1986 and 1996, 147 patients underwent valve replacement combined with coronary artery bypass grafting. The mitral valve was replaced in 104 patients, the aortic valve in 34, and both mitral and aortic valves were replaced in 9. One hundred and twenty-two (83%) were male with a mean age of 56 ± 5 years (range, 38 to 77 years). The mean age for female patients was 57.9 ± 5 years (range, 38 to 70 years). All of the patients had rheumatic valve disease. Preoperatively, 68% were in New York Heart Association functional class III or IV and 32% were in class II. A total of 252 distal anastomoses were performed (mean, 1.71 per patient) in these patients of whom 48.9% had single-vessel disease, 45% had two-vessel or three-vessel disease, and 6.1% had left main coronary artery disease. The hospital mortality rate was 10.2%. Three patients died during the follow-up period and the overall actuarial survival rate at 10 years was 96.6% ± 1.9%. Operations that combine both valve replacement and coronary artery bypass are performed more frequently because perioperative risk has decreased through more effective myocardial protection. If untreated, both coronary artery disease and significant valve disease may reduce patient survival.

Mitral Valve Replacement with Bioprosthesis in Age Group Fifty to Sixty-Five Years

Between 1982 and 1990, 151 patients aged 50 to 65 years of age underwent isolated mitral valve replacement with a bioprosthesis. Overall hospital mortality was 10.6% (16/151). The total cumulative follow-up period was 527.6 patient-years with a mean of 4.34 ± 2.53 years and a range of 2 months to 10.9 years. During the follow-up period, 27 patients (5.11% per patient-year) developed bioprosthesis dysfunction of whom 26 were reoperated and one was treated medically, 4 patients had thromboembolic complications (0.75% per patient-year), one patient (0.18% per patient-year) had anticoagulant-related bleeding, and two patients (0.37% per patient-year) had a paravalvular leak (one was reoperated). Total valve-related complications were 6.44% per patient-year. Late mortality was 2.65% per patient-year (14/151). Ten-year actuarial survival was 78.5%. Freedom from bioprosthesis dysfunction was 56.6%, from thromboembolic complications 95.8%, and from all complications 49.6%. Our findings of a high rate of bioprosthesis dysfunction as well as a low rate of thromboembolic complications after mitral valve replacement with a bioprosthesis in older patients suggests that the use of bioprostheses should be limited.

Long-term results of reconstructions of the left anterior descending coronary artery in diffuse atherosclerotic lesions

One hundred twenty patients who had diffuse atherosclerotic lesions necessitating reconstruction of the left anterior descending artery with or without open endarterectomy and coronary artery bypass grafting were investigated retrospectively and compared with 130 patients who underwent conventional bypass grafting in the same time frame.

METHODS

Sixty-one endarterectomies were performed with long arteriotomies (group I) and 59 patch reconstructions were placed over stenosing plaques without an endarterectomy (group II). Patients having only conventional coronary bypass constituted group III.

RESULTS

Hospital mortalities were 6.5%, 5.1%, and 1.5% in group I, group II, and group III, respectively (p = not significant). Five patients in group I (8.1%), six in group II (10.1%), and two in group III (1.5%) had perioperative myocardial infarction (group II vs group III, p = 0.016). Angiographic restudy of grafts to the left anterior descending system revealed a patency rate of 81.5% in group I, 79.1% in group II, and 94.4% in group III patients after mean periods of 6.3, 5.7, and 6.1 years, respectively (p = not significant). Actuarial survivals at 7 years were 94% +/- 5.0%, 74.8% +/- 16%, and 90.9% +/- 7.4% in groups I, II, and III, respectively (group I vs group II, p = 0.007; group II vs group III, p = 0.008). Freedom from recurrent angina at 7 years was 42.7% +/- 15.6% in group I, 33.5% +/- 19% in group II, and 71.9% +/- 14.2% in group III (group I vs group III, p = 0.03; group II vs group III, p = 0.0001). Thirty-four percent of patients in group I, 24% in group II, and 60.4% in group III were working actively in the late postoperative period (p = 0.0001).

CONCLUSION

Extended revascularizations of the left anterior descending coronary artery increase surgical risk, although not to a statistically significant degree, and should be performed only of necessity. However, once needed, revascularization is a lifesaving procedure with acceptable early and long-term results.

A prospective study of the survival of chemically activated anterior resin composite restorations in general dental practice: 5-year results

The principals of 26 general dental practices agreed to use six chemically activated resin composite restorative materials to restore Class III and Class V lesions and record information concerning their performance over a period of 5 years. The information collected was analysed by actuarial methods to assess the clinical longevity and reasons for replacement as perceived by the dentists operating in the General Dental Service in England. At the end of 5 years, 14 dentists provided sufficient returns for their data to be considered suitable for analysis. The database consisted of 2399 Class III and 1093 Class V restorations. The overall probability of survival at 5 years of Class III and Class V restorations was 62.9% and 71.8% respectively. The difference in performance between the six restorative materials was small, with the probability of survival varying from 70.4 +/- 2.9% to 56.3 +/- 2.9% for the Class III restorations and 78.6 +/- 3.7% to 67.7 +/- 4.2% for the Class V restorations. The main reasons for replacement were general surface discoloration, secondary caries and fracture. The chemically activated composite restorative materials available at the time of initiating this study produced comparable performances in general dental practice when used without enamel and dentine bonding techniques. This suggests that more general practice-based clinical studies are needed to determine whether or not improvements in materials and techniques are effectively transferred to the general practice situation.

Clinical performance of low-profile bioprostheses: results at 10 years

The purpose of this retrospective study is to evaluate the long-term performance of the Liotta minimally intrusive bioprosthesis (MIB) and to identify its most important risk factors. From January 1980 to March 1982, 73 patients (30 males and 43 females; mean age 45.5 years +/- 11.7 standard deviation; range 11 to 64) underwent operation for heart valve replacement with an MIB. Fifty-two mitral valve replacements (MVR), 16 aortic valve replacements (AVR), 4 mitral and aortic valve replacements (MAVR), and 1 mitral and tricuspid valve replacement (MTVR) have been performed (78 MIBs implanted). Global operative mortality has been 8.2% (6/73): 9.6% (5/52) for MVR and 6.2% (1/16) for AVR. The 10-year follow-up reaches 519 patient-years and 581 valve-years, and is 96.5% and 93.9% complete, respectively. Actuarial freedom from any patient- or valve-related event has been calculated at one time with its hazard function and its incidence normalized per 100 patient- and/or valve-years; statistical significance of difference between curves has been assessed. In this report, overall actuarial survival at 10 years is 79.4% +/- 5.3% SEM (standard error of the mean), including operative deaths (incidence = 2.6% per patient-year). Two patients experienced periprosthetic leakage (PL) at 4 and 9 years, respectively (incidence = 0.4% per valve-year). One patient underwent reoperation because of otherwise untreatable prosthetic valve endocarditis (PVE) at 5 years (0.2% per valve-year).(ABSTRACT TRUNCATED AT 250 WORDS)

Viable and nonviable aortic homografts in the subcoronary position: a comparative study

One hundred fifty-five freeze-dried, 63 frozen, and 337 Hanks'-antibiotic solution preserved or nutrient-antibiotic solution preserved homografts used for isolated aortic valve replacement have been followed for 1 to 20 years (mean, 5.3 years), a total of 2,931 patient-years of follow-up information. Overall survival, valve-related death, primary tissue failure, failure due to surgical technical error, infective endocarditis, and overall event-free survival have been assessed and compared. Overall survival 20 years after operation was 51.6% +/- 8.1% with a low incidence of sudden death. The method and length of preservation did not have any effect on the long-term performance or the mode of failure of the homografts. The rate of primary tissue failure was apparently higher with valves preserved in a solution containing calf serum, but the difference was not significant. It is concluded that long-term patient survival and quality of life after aortic valve replacement with a homograft are excellent. The current study, however, could not verify the existence of a significant difference between the three assessed methods of homograft preservation. Furthermore, it could not prove the importance of cellular viability or the existence of clinically significant immunological factors other than the calf serum content of the nutrient medium.

Valve replacement in children: guidelines for selection of prosthesis and timing of surgical intervention

One hundred fifty-nine patients ranging from 3 months to 18 years old (mean, 8.1 +/- 3.7 years) underwent 162 primary valve implantations. A porcine valve was used in 104 patients, a St. Jude Medical valve in 40, and a Björk-Shiley valve in 18. The valve replaced was the aortic in 25 patients, the mitral (systemic atrioventricular [AV] valve) in 43, the pulmonary in 71, and the tricuspid (pulmonary AV valve) in 23. Hospital mortality was 6%. Patients with a Björk-Shiley valve received warfarin sodium anticoagulation, and those with a St. Jude Medical valve were given salicylates and dipyridamole. Follow-up is available on all patients 0.6 to 12 years postoperatively (mean, 6.3 +/- 2.6 years). New York Heart Association Functional Class improved in 62% and remained unchanged in 38% of the patients. Thromboembolic complications occurred in only 8 (57%) of 14 patients with a St. Jude Medical valve in the right (pulmonary) side and in 3 (12%) of 26 with the valve in the left (systemic) side of the circulation. Bacterial endocarditis developed in 3 patients, all with porcine valves. Early valve replacement, less than 2 years after detection of hemodynamic deterioration, resulted in improvement in the ventricular ejection fraction in 25 of 29 patients (from 81 +/- 14% to 90 +/- 12% of normal; p less than 0.05). In contrast, the ejection fraction remained abnormal in all 22 patients with delayed valve insertion (more than 2 years) (81 +/- 16% of normal preoperatively and 80 +/- 10% of normal following operation; p = not significant).

Long-term results of porcine valve insertion for pulmonary regurgitation following repair of tetralogy of Fallot

Between January 1975 and January 1985, 49 patients, aged 2 to 20 years, underwent porcine valve insertion for control of pulmonary regurgitation following repair of tetralogy of Fallot. In 9 patients the valve was placed at the time of the repair; in the remaining 40, valve insertion was performed 2 to 5 years postoperatively. The primary indications for valve implantation included progressive cardiomegaly and evidence of right ventricular (RV) dilatation or dysfunction. Operative technique emphasized ample enlargement of the RV outflow tract and main pulmonary artery to allow for insertion of a large valve and prevention of turbulence or stenosis. There was 1 hospital death (2%). Follow-up is available on remaining patients 1 to 10 years postoperatively. Considerable prosthetic valvar stenosis or regurgitation occurred in 7 patients (14%) 3 to 8 years following insertion, including one after subacute bacterial endocarditis. The complication-free actuarial life was 82%, and the functional actuarial life was 84% at 10 years for the prosthesis. The data suggest that the porcine valve has a good long-term durability when inserted in the pulmonary position in pediatric patients.

Five-year clinical evaluation of the St. Jude Medical valve prosthesis in 136 patients

One hundred and thirty-six patients (June 1979, through May 1984) underwent mitral, aortic or double valve replacement and apico-aortic bypass with the St. Jude Medical (SJM) prosthesis, at Ryukyu University Hospital, Okinawa. Operative mortality for the entire group was 4.4 per cent. Late mortality from 1979-1984 was 6.1 per cent. There were no deaths related to mechanical failure. Warfarin anticoagulation was recommended for all patients. The incidence of thromboembolism was 0.76/100 patient years. Post operative catheterization studies in 21 patients one year after operation showed a satisfactory recovery of cardiac function. The SJM valve seems to be the satisfactory artificial valve in present use.

Porcine cardiac bioprostheses: evaluation of long-term results in 990 patients

Clinical results with porcine bioprostheses were reviewed for 990 patients who underwent heart valve replacement from January, 1974, to December, 1980. Eight hundred and seventy-four Hancock, 283 Carpentier-Edwards, and 10 Liotta bioprostheses were used. In 23 patients, 26 mechanical prostheses were implanted as well. Overall operative mortality was 60 out of 990 (6.06%): 30 out of 506 (5.9%) for mitral valve replacement (MVR), 13 out of 287 (4.5%) for aortic valve replacement (AVR), 1 out of 4 (25%) for tricuspid valve replacement, 0 out of 2 for pulmonary valve replacement, and 16 out of 191 (8.4%) for multiple valve replacement. Cumulative follow-up covered 1,793 patient-years. (Actuarial survival at 7 years was 76.6 +/- 3% for MVR. At 6 years, it was 83.2 +/- 2.8% for AVR and 55 +/- 13.5% for multiple valve replacement.) Prosthesis-related survival at 7 years was 91.7 +/- 1.9% for MVR, and at 6 years, it was 96.6 +/- 1.5% for AVR and 95.1 +/- 2.2% for multiple valve replacement. Bioprosthesis survival, considering deaths or complications that led to reoperation as final events, was 84.2 +/- 3.7% at 7 years for mitral valves and 87.7 +/- 3.8% at 6 years for aortic valves. Emboli per 100 patient-years numbered 3.2 for MVR, 0.5 for AVR, and 1.6 for multiple valve replacement. Twenty-seven patients underwent reoperation, 12 for perivalvular leak, 5 for endocarditis, 6 for valve thrombosis, and 4 for primary tissue failure (linearized rates of 0.7, 0.3, 0.3, and 0.2% per patient-year, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Late results of mitral valve replacement using unstented antibiotic sterilised aortic homografts

Three hundred and seventy nine patients who had undergone mitral valve replacement using unstented antibiotic sterilised aortic homografts were followed up for 52 to 138 months (mean 102 months). Patients requiring additional aortic valve replacement were excluded. The commonest cause was rheumatic heart disease (321 patients). There were 37 early deaths (9.8%) and 97 late deaths (28%). The actuarial survival of operative survivors was 83% at three years, 75% at five years, and 55% at nine years. Technical valve failure occurred in six patients (1.6%), infective endocarditis in 19 (5%), and degeneration of the valve in 43 (12.5%). The cumulative probability of freedom from endocarditis was 96% at three years, 94% at five years, and 91% at nine years, while that of freedom from valve degeneration was 97% at five years and 48% at 10 years. There were no early embolic episodes, but late embolism occurred in five patients (1.5%).

Assessment and comparison of the performance of cardiac valves

A statistical method is presented to assess and compare cardiac valve performances. Patient survival and valve performances have been separated, and valve function and malfunction have been described in comprehensive and comparable terms. Formulas are proposed to calculate the significance of the difference between two survival probabilities as well as to calculate the instantaneous rate of events and the median remaining lifetime.

Aortic valve replacement with Starr-Edwards valves over 14 years

Three hundred thirteen patients underwent aortic valve replacement with 319 Starr-Edwards caged-ball prostheses and have been followed for 1 to 14 years. Hospital mortality (24.8%) and first-year mortality (4.8%) suggest that this is a high-risk group. Overall postoperative patients survival was 37.1%, with 18.8% free from any event, at 14 years. Thromboembolism was the most significant single event (a probability of 18.7% at 14 years), and the Series 2300/2320 valves were associated with a probability of hemolysis of nearly 80% over 13 years. Patients who underwent valve replacement before 1973 had a significantly greater probability of late death (31.1%) and of complications (47.1%) during the first 5 years. Those patients undergoing replacement after 1973 had a significantly greater probability of thromboembolic episodes (15.4%). Starr-Edwards cage-ball prosthesis provide an acceptable valve replacement for high-risk patients. However, the overall complication rate of 81.2% over 14 years, compared with 78% for homograft valves for the same period, does not support the adoption of this prosthesis as the valve of first choice at this hospital.