Current issues of ACP Journal Club are published in Annals of Internal Medicine


Therapeutics

Long-term survival was similar for mechanical heart valves and bioprostheses although some adverse effects differed

ACP J Club. 1993 Sept-Oct;119:41. doi:10.7326/ACPJC-1993-119-2-041


Source Citation

Hammermeister KE, Sethi GK, Henderson WG, et al. A comparison of outcomes in men 11 years after heart-valve replacement with a mechanical valve or bioprosthesis. N Engl J Med. 1993 May 6; 328:1289-96.


Abstract

Objective

To compare mortality and valve-related complications in men who had received either a mechanical heart valve or a porcine bioprosthetic valve.

Design

Randomized controlled trial with a mean follow-up of 11 years.

Setting

13 Veterans Affairs medical centers.

Patients

575 men (mean age at entry 59 y, 76% in New York Heart Association functional class III or IV, 44% with coronary heart disease). Inclusion criteria were need for aortic-valve or mitral-valve replacement, no previous valve replacement, no active endocarditis, no contraindications to warfarin, a diameter of ≥ 21 mm available for aortic prostheses or ≥ 27 mm for mitral prostheses, and a life expectancy, exclusive of cardiac disease, of ≥ 3 years. Follow-up was > 99%.

Intervention

Randomization was done in the operating room. For aortic valve replacement, 198 men received mechanical prostheses and 196 received bioprostheses. For mitral valve replacement, 88 men received mechanical prostheses, and 93 received bioprostheses. Bjork-Shiley spherical-disk valves and Hancock porcine-heterograft bioprosthetic valves were used.

Main outcome measures

Death from any cause and valve complications: systemic embolism, clinically important bleeding, prosthetic-valve endocarditis, nonthrombotic valve obstruction, perivalvular regurgitation, or reoperation.

Main results

The groups did not differ for operative mortality (8% overall and 11% for patients with coronary artery disease) or for 11-year mortality (57% for mechanical valves vs 62% for bioprostheses). No statistically significant differences were found for total valve-related complications, systemic embolism, endocarditis, valve thrombosis, perivalvular regurgitation, or reoperation. Patients with mechanical valves compared with those with bioprostheses had a higher probability of clinically significant bleeding episodes (43% vs 24% for aortic valves [P < 0.001] and 41% vs 28% for mitral valves [P = 0.02]) and a lower probability of structural valve failure (0% vs 15% for aortic valves and 0% vs 36% for mitral valves [P < 0.001 for both comparisons]).

Conclusions

The mechanical-valve and bioprostheses groups did not differ for operative or long-term mortality or total valve-related complications. Patients who received mechanical valves had a higher rate of bleeding episodes and a lower rate of structural valve failure compared with patients receiving bioprostheses.

Source of funding: Department of Veteran Affairs Medical Research Service.

For article reprint: Dr. K.E. Hammermeister, Cardiology Section (111B), Veterans Affairs Medical Center, 1055 Clermont, Denver, CO 80220-3877, USA. FAX 303-393-4656 (Only for requests from outside North America.)


Commentary

No artificial heart valve can match a normal native valve in performance (hemodynamics, durability, low thrombogenicity, and high resistance to infection). Because of the shortcomings of artificial valves, the major clinical dilemmas are when to replace a diseased value and which artificial valve to use. 2 randomized trials of tissue and mechanical valves have now been done: the Edinburgh trial (1) and the Veteran Affairs (VA) trial by Hammermeister and colleagues summarized here. At first glance, results from the 2 studies disagree. The mechanical valve had fewer overall complications in the Edinburgh trial (1), but equivalent overall complications in the VA study. On closer inspection, however, both trials found mechanical valves were more durable (fewer valve failures and reoperations), and tissue valves were associated with less bleeding. The relative incidence of different valve complications in the 2 studies led to the apparent disagreement, mostly because of higher rates of bleeding in the VA study. A key difference is that the VA study used a more intense anticoagulation regimen (prothrombin time ratio 2.0 to 2.5) than is currently recommended (ratio 1.5 to 2.0). A recent randomized trial in patients with prosthetic valves showed a prothrombin time ratio of 1.5 yields the same rates of thromboembolism as a ratio of 2.5 but with fewer bleeding complications (2).

My reading of the evidence is that a mechanical valve with a low-intensity anticoagulation regimen is generally better, except when anticoagulation would be riskier than usual or the patient prefers to avoid anticoagulation (e.g., plan for pregnancy).

Mark A. Hlatky, MD
Stanford UniversityStanford, California, USA

Mark A. Hlatky, MD
Stanford University
Stanford, California, USA


References

1. Bloomfield P, Wheatley DJ, Prescott RJ, Miller HC. Twelve-year comparison of a Bjork-Shiley mechanical heart valve with porcine bioprostheses. N Engl J Med. 1991;324:573-9.

2. Saour JN, Sieck JO, Mamo LA, Gallus AS. Trial of different intensities of anticoagulation in patients with prosthetic heart valves. N Engl J Med. 1990; 322: 428-32.


Editorial Comment

The widely accepted recommendations for anticoagulation in patients with mechanical valves suggest targeting INR (international normalized ratio) levels of 2.5 to 3.5 (3, 4) for bileaflet and tilting disk mechanical valves are based primarily on observational studies. Aspirin, 80 to 100 mg/d, in addition to oral anticoagulation has been shown to decrease vascular mortality but is associated with increased risk for infections (5).

3. Stein PD, Alpert JS, Copeland J, et al. Antithrombotic therapy in patients with mechanical and biological prosthetic heart valves. Chest. 1995 Oct; 108(4 Suppl): 371-9S.

4. Acar J, Iung B, Boissel JP, et al. AREVA: multicenter randomized comparison of low-dose versus standard-dose anticoagulation in patients with mechanical prosthetic heart valves. Circulation. 1996; 94(9): 2107-2112.

5. Turpie AG, Gent M, Laupacis A, et al. A comparison of aspirin with placebo in patients treated with warfarin after heart-valve replacement. N Engl J Med. 1993;329:524-9.