The superiority of cold oxygenated dilute blood cardioplegia.

It has been clearly shown, both in a laboratory model and in humans, that oxygenation of crystalloid cardioplegic solutions markedly enhances myocardial preservation. The addition of a small volume of red cells to a crystalloid perfusate improves capillary perfusion. Based on these results, we have changed our cardioplegic solution from cold crystalloid to cold oxygenated dilute blood. In the present study we retrospectively evaluate the results of 400 operative procedures to determine whether the addition of oxygenation and a small volume of blood to the cardioplegic solution enhances myocardial protection in the clinical setting. Two hundred consecutive patients who underwent operation with cardioplegic arrest using a cold crystalloid cardioplegic solution (group 1) were compared with a subsequent 200 patients who underwent operation with cold oxygenated dilute blood cardioplegia (group 2). Patients in group 2, who received cold oxygenated dilute blood cardioplegia, had a significantly reduced need for postoperative intraaortic balloon pump counterpulsation and for atrioventricular pacing. Also, patients in group 2 had a lower incidence of perioperative myocardial infarction and had improved early outcome. None of the 200 patients in group 2 had electrocardiographic evidence of perioperative infarction. We conclude that cold oxygenated dilute blood cardioplegia provides better preservation than does a nonoxygenated crystalloid solution during elective ischemic arrest, because a cold crystalloid solution is able to deliver oxygen and the red cells are able to enhance capillary perfusion.

Prosthetic valve endocarditis. Analysis of factors affecting outcome of therapy.

We analyzed the outcome of 116 patients with prosthetic valve endocarditis treated between 1975 and 1983 and used multivariate analysis to identify risk factors for in-hospital mortality and bad outcome during follow-up. Complicated prosthetic valve endocarditis was defined as the presence of a new or changing heart murmur, new or worsening heart failure, new or progressive cardiac conduction abnormalities, or prolonged fever during therapy. Complicated prosthetic valve endocarditis was present in 64% of patients; factors associated with complicated prosthetic valve endocarditis included aortic valve infection (odds ratio 4.3, p = 0.002) and onset of endocarditis within 12 months of the cardiac operation (odds ratio 5.5, p = 0.0001). The in-hospital mortality rate for prosthetic valve endocarditis was 23%; patients with complicated prosthetic valve endocarditis had a higher mortality than patients with uncomplicated infection (odds ratio 6.4, p = 0.0009). Combined medical-surgical therapy was used in 39% of patients; surgical therapy was more common in patients with complicated prosthetic valve endocarditis (odds ratio 16, p less than 0.0001) and in patients infected with coagulase-negative staphylococci (odds ratio 3.9, p = 0.003). Survival after initially successful therapy for prosthetic valve endocarditis was adversely affected by the presence of moderate or severe congestive heart failure at hospital discharge (p = 0.03). Bad outcome during follow-up (death, relapse of prosthetic valve endocarditis, or subsequent cardiac operation related to sequelae of the original infection) was more common in the medical than the medical-surgical therapy group (p = 0.02). The difference in long-term outcome between patients treated initially with medical or with medical-surgical therapy was particularly evident in those with complicated prosthetic valve endocarditis (p = 0.008). The presence of complicated prosthetic valve endocarditis is a central variable in assessing prognosis and planning therapy; the majority of patients with complicated prosthetic valve endocarditis are best treated with medical-surgical therapy. Those who are not treated surgically during their initial hospitalization are at high risk for progressive prosthesis dysfunction and require careful follow-up.

Risk factors for the development of prosthetic valve endocarditis.

Risk factors for the development of prosthetic valve endocarditis (PVE) were analyzed in 2642 patients undergoing initial valve replacement at the Massachusetts General Hospital from 1975 to 1982. Follow-up was available for 2608 patients (98.7%); the mean length of follow-up was 39.8 months. PVE developed in 116 patients (4.4%). The actuarial risk of PVE was 3.1% at 12 months and 5.7% at 60 months. A Cox model was used to identify risk factors for PVE. Recipients of multiple valves had a higher risk of PVE than single valves (p = .01). There was no difference in the risk of PVE for patients receiving aortic valves vs those receiving mitral valves. Recipients of mechanical valves had a higher risk of PVE than recipients of porcine valves in the first 3 months after surgery (p = .02), but the risk of PVE was higher for porcine valve recipients 12 months or more after surgery (p = .004). Despite this difference in the time course of development of PVE, there was no significant difference in the cumulative risk of PVE by 5 years of follow-up between mechanical and porcine valve recipients. Male sex was a risk factor for PVE within 12 months of aortic valve replacement (p = .008) but not thereafter; sex did not influence the risk of PVE after mitral valve replacement. Older patients had a higher risk of late PVE after multiple (p = .04) or mitral valve replacement (p = .08), but not after aortic valve replacement.