Bicarbon valve -- European multicenter clinical evaluation

OBJECTIVE

Fifteen collaborating centers in eight countries present their pooled experience with the new Bicarbon bileaflet valve.

METHODS

Between 4/90 and 4/96, 1351 patients, 806 males and 545 females, aged 10 to 83, mean 58.4 +/- 12.4, underwent valve implantation.

OPERATIONS

aortic valve replacement (AVR), 726; mitral valve replacement (MVR), 475; double valve replacement (DVR), 150. Additional procedures: CABG, 211; TV repair, 64; other, 152.

RESULTS

Mortality: 67 early (seven valve related) and 56 late (40 valve related). Valve thrombosis: six obstructive, three non-obstructive; embolism: nine major cerebral, 37 other. Major bleeding: 29. Hemolysis: two clinically significant. Non-structural dysfunction: 24 paravalvular leaks, one leaflet interference. No structural failure! Endocarditis: 24. Reoperation 48: 22 non-structural dysfunctions, 14 endocarditis, seven thrombosis and embolism, five other. Estimated 5-year freedom from valve-related deaths is 97.2% for AVR and 92.4% for MVR; 4-year freedom from valve related deaths for DVR is 90.5%. Mean calculated NYHA improvement is 1.24.

CONCLUSIONS

The Bicarbon mechanical prosthesis is well designed, durable, has good hemodynamic features and an acceptably low incidence of complications.

Mediastinitis in patients undergoing cardiopulmonary bypass: risk analysis and midterm results

BACKGROUND

Deep sternal wound infection (mediastinitis) occurred in 21 out of 4043 consecutive patients who underwent a cardiopulmonary bypass procedure (incidence of 0.4%).

METHODS

Clinical characteristics of patients who developed mediastinitis (group I) were compared to those of patients who had no mediastinal infection (group II).

RESULTS

Hospital mortality was significantly higher in group I (14% vs 3.8%) (p<0.001). Mean hospital stay was longer in group I (36 days vs 7 days) (p<0.001). Multivariate analysis identified the following variables as significant risk factors for developing postoperative mediastinitis: diabetes; relative risk (RR)=3.02, 95% confidence limits (CL)=1.68-5.45, resternotomy for bleeding: RR=5.43, CL=1.85-15.92, associated leg wound infections; RR=16.55, CL=5.32-51.49, the need for 3 or more units of blood transfusion; RR=2.48, CL=1.82-3.39, obesity; RR 4.96, CL 2-12.25. Group I patients were categorised according to a recently proposed classification for mediastinitis (reference 1). Type I (n=17), mediastinitis presenting within 2 weeks following surgery in the absence of risk factors. Type II (n=2), mediastinitis presenting at 2-6 weeks following surgery in the absence of risk factors. Type IIIA (n=2), mediastinitis type I in the presence of one or more risk factor(s). Wound debridement and closed mediastinal irrigation was performed in 19 patients; 15 cases with type I, 2 with type II, and 2 with type IIIA. Primary closure without irrigation was performed in 2 type I patients. The primary intervention failed in 3 patients, two of whom died. A third patient died 4 weeks after an apparently successful treatment of type I mediastinitis. Midterm follow-up (mean of 18 months) of 18 patients showed that 16 patients were alive and well, there was one late death, and one patient had chronic wound pain.

CONCLUSION

Diabetes, obesity, associated leg-wound infection, and the need for repeated blood transfusions are associated with high risk of mediastinitis. Closed mediastinal irrigation for mediastinitis type I can yield satisfactory functional and cosmetic midterm results.

Intermittent ischaemic arrest and cardioplegia in coronary artery surgery: coming full circle?

OBJECTIVE

To compare the cardioprotective efficacy of cold crystalloid cardioplegia and intermittent ischaemic arrest in patients undergoing elective coronary artery surgery.

DESIGN

Prospective randomised trial.

SETTING

London teaching hospital.

SUBJECTS

20 patients with at least moderately good left ventricular function undergoing elective coronary artery surgery by one experienced surgeon and needing at least two bypass grafts.

INTERVENTIONS

Patients were randomised to cold crystalloid cardioplegia or intermittent ischaemic arrest.

MAIN OUTCOME MEASURES

The primary determinant of the efficacy of myocardial protection was serial measurement (before and at 1, 6, 24, and 72 hours after the end of cardiopulmonary bypass) of cardiac troponin T (cTnT), a highly sensitive and specific marker of myocardial damage.

RESULTS

There was no significant difference in age, ejection fraction, number of grafts, bypass times, or cross clamp times between the two groups. One patient in the cardioplegia group had a perioperative infarct and was excluded from further study. In both groups there was a significant increase in cTnT, with peak concentrations being reached 6 hours after the end of cardiopulmonary bypass and remaining significantly high at 72 hours. At 6 hours the median (75% interquartile range) concentrations of cTnT were similar in both groups (1.8 (1.0-3.6) micrograms/l for cardioplegia v 1.9 (1.0-3.5) micrograms/l for intermittent ischaemic arrest).

CONCLUSION

This trial shows that intermittent ischaemic arrest, even without systemic cooling or venting of the left ventricle, provides a similar level of myocardial protection to cardioplegia in patients with moderate left ventricular function and short ischaemic times.

Lack of cardioprotective efficacy of allopurinol in coronary artery surgery

OBJECTIVE

To examine the cardioprotective efficacy of allopurinol in patients undergoing elective coronary artery surgery.

DESIGN

Prospective randomised trial.

SETTING

London teaching hospital.

PATIENTS

Twenty patients with at least moderately good left ventricular function undergoing elective coronary artery surgery and requiring at least two bypass grafts.

INTERVENTIONS

Patients were randomised to receive allopurinol (1200 mg in two divided doses) or to act as controls.

MAIN OUTCOME MEASURE

The primary determinant of the efficacy of myocardial protection was serial measurement (preoperatively and subsequently at one, six, 24, and 72 hours after the end of cardiopulmonary bypass) of cardiac troponin T (cTnT) a highly sensitive and specific marker of myocardial damage. Additional evidence was provided by serial measurement of the MB-isoenzyme of creatine kinase (CK-MB) and myoglobin, ECG changes, and clinical outcome.

RESULTS

There was no significant difference in age, ejection fraction, number of grafts, bypass times, or cross clamp times between the two groups. In both groups there was a highly significant (p < 0.01) rise in cTnT, CK-MB, and myoglobin. Peak concentrations were reached between one (CK-MB and myoglobin) and six hours (cTnT) after the end of cardiopulmonary bypass. At 72 hours cTnT concentrations were six times higher than baseline concentrations whereas CK-MB and myoglobin were approximately double baseline concentrations. There was no significant difference in cTnT, CK-MB, or myoglobin between the allopurinol and control groups at any time. There was no diagnostic ECG evidence of perioperative infarction in any patient.

CONCLUSION

Unlike previous reports this study did not show that allopurinol had a cardioprotective effect in patients with good left ventricular function undergoing elective coronary artery surgery.

Ventricular septal rupture complicating myocardial infarction: is earlier surgery justified?

Fifty-five consecutive cases of ventricular septal rupture following myocardial infarction were reviewed in order to ascertain clinical and haemodynamic determinants of in-hospital mortality. Factors associated with a poor prognosis included clinical evidence of a poor haemodynamic state or biochemical evidence of impaired renal function. Twenty-six patients managed before 1982 (group 1) were then compared with 29 managed subsequently (group 2) when a policy of earlier surgical intervention had been adopted. Patients in group 2 were more haemodynamically compromised and had greater impairment of renal function. The surgical mortality in group 1 was 3 of 18 patients (17%) which was not significantly different from that in group 2 (7 of 22 patients, 32%). Earlier surgical intervention in ventricular septal rupture is frequently undertaken in critically ill patients whose prognosis is poor. However their surgical risk is not significantly increased and such an approach can therefore be justified as it may salvage some patients who otherwise would not survive.

Randomised placebo controlled trial of aspirin and dipyridamole in the prevention of coronary vein graft occlusion

Treatment with the combination of aspirin and dipyridamole is believed to reduce the incidence of coronary vein graft occlusion. A double blind randomised controlled trial was carried out in which aspirin 990 mg and dipyridamole 225 mg daily or placebo were added to the routine postoperative management (warfarin for three months) of 320 patients undergoing coronary bypass grafting. The trial treatment was given for 12 months, after which the results were assessed by coronary and graft angiography. The two randomised groups, each of 160 patients, were comparable in age, sex, symptomatic state, angiographic findings, and operative procedure. Repeat coronary arteriography was carried out on 266 patients, 133 in each group. All grafts and distal anastomoses were patent in 68% (91/133) of the placebo patients and in 75% (100/133) of those receiving active treatment. Overall graft patency was 87% (306/352) and 89% (342/385) respectively. Retrospective subgroup analysis showed patency rates of 72% (26/36) and 78% (39/50) of grafts to vessels requiring preliminary endarterectomy, and 80% (36/45) and 91% (40/44) of distal anastomoses to vessels measured at operation to have a diameter of less than or equal to 1 mm. None of these differences was significant at the 5% level. Thus in this group of patients with high graft patency rates, treatment with aspirin and dipyridamole conferred no appreciable advantage.

Different mechanisms for the relief of angina after coronary bypass surgery. Physiological versus anatomical assessment

To determine the physiological effect of coronary artery bypass surgery and the mechanisms for pain relief, 15 patients with exertional angina were studied before and after operation. Before the operation conventional tests included exercise tests (all positive) and coronary angiography (all patients had greater than or equal to 70% stenosis of major vessels). In addition, ambulatory electrocardiographic monitoring during 48 hours detected 92 episodes (greater than or equal to 1 mm) of ST depression. Regional myocardial perfusion was assessed with positron tomography using rubidium-82 (t1/2 78 s) and this showed reversible inhomogeneity with absolute regional reduction of cation uptake after exercise in all 15 patients. After coronary surgery 10 of the 15 patients had (a) no angina, (b) patent grafts (three or more), (c) no evidence of ischaemia during ambulatory monitoring out of hospital, and (d) homogeneous perfusion with reversal of the disturbances in regional myocardial perfusion after exercise. After operation one of the 15 patients had no angina and showed silent infarction in the segment that was previously ischaemic but supplied by a patent graft. All but one of the remaining patients had no angina, patent grafts, but disturbances of regional myocardial perfusion with silent ischaemia on exercise. Two of these patients continued to have asymptomatic and ischaemic episodes of ST depression during ambulatory monitoring out of hospital. This physiological study of regional myocardial perfusion in patients in hospital and in those with ischaemia out of hospital showed that three different mechanisms may account for the relief of pain--improved perfusion, infarction, and silent ischaemia. Silent ischaemia in particular raises puzzling pathophysiological and therapeutic questions that may affect prognosis and the interpretation of clinical trials.

Safety and effectiveness of a portable external automatic defibrillator-pacemaker

Sudden cardiac death in the community can be reduced by early resuscitation. The commonest arrhythmia encountered in this setting is ventricular fibrillation. A portable external automatic defibrillator-pacing machine for use by emergency services and laymen after basic training, has recently been introduced. This device has a tongue-abdominal pathway for sensing the electrocardiogram and respiration, as well as delivery of current. In its automatic mode, the machine cannot defibrillate unless the patient's breathing and gag reflex are virtually absent. The decision-making characteristics of the machine were defined in isolation from the patient using simulated ECG signals and recordings of arrhythmias obtained during cardiac surgery and during electrophysiological studies. The pathway was evaluated separately by attaching it to a conventional defibrillator and using it in the elective cardioversion of 15 patients. Electrode sites were examined and creatine phosphokinase (CPK) and creatinine phosphokinase isoenzyme (CPKMB) release determined following conversion. Repeated playback of the same 34 minutes of selected recordings showed that decisions were consistent 95% of the time. Automatic pacing always occurred with asystole. ECG signals less than 0.35 mV in amplitude were not recognized, but a manual override switch could be operated in those circumstances where there was failure to act upon fine ventricular fibrillation. Defibrillation of 50% of the recordings of supraventricular and ventricular tachycardia did occur, but this could not have happened in practice unless the patient was unconscious, and in addition, the operator failed to countermand this decision. The tongue-abdominal pathway yielded good recordings of the ECG.(ABSTRACT TRUNCATED AT 250 WORDS)

Collagen content of atherosclerotic arteries is higher in smokers than in non-smokers

The biochemical composition of coronary endarterectomy and aortic samples obtained during 52 coronary artery bypass graft operations was analysed. The content of cholesterol or collagen relative to protein in the aorta or endarterectomy specimens did not correlate with serum total cholesterol, triglyceride, or high-density-lipoprotein cholesterol, nor were there any significant differences between samples from normotensive and hypertensive patients. However, smokers had a significantly higher content of collagen in coronary endarterectomy specimens and the aorta and a higher content of cholesterol in the aorta than non-smokers.