Bacteraemia in ventricular assist devices: a common complication that need not affect clinical outcomes.

BACKGROUND: Ventricular assist device (VAD) implantation has become an effective option for patients with severe heart failure. However, device-related infections remain a significant problem. The aim of this study was to describe the incidence and microbiological aetiology of bacteraemia in patients with VADs, and to assess the impact of bacteraemia on clinical outcomes. METHODS: A retrospective study was conducted of patients having VAD implantation at the Alfred Hospital (Melbourne, Australia) from October 1990 to July 2009. Medical records and microbiology databases were reviewed. Patients who were supported with a VAD for 72h or more were evaluated for demographic data, VAD type, the occurrence of bacteraemia and clinical outcomes. RESULTS: During the 19-year period, 135 VAD patients (89 Thoratec PVAD, 10 Novacor, and 36 Ventrassist) supported for a total duration of 17,304 (median 74) support days were included. Sixty-one patients (45%) developed VAD-associated bacteraemia, an incidence of 5.6 episodes per 1000 support days. The incidence of bacteraemia per 1000 days of support was similar for the three devices used: Thoratec PVAD, Novacor and Ventrassist VADs (7.8±0.8, 5.2±1.5 and 3.4±0.5, respectively, p=0.74). Staphylococcus aureus was the most common pathogen (25%). The rates of death on device, survival to transplant, recovery with explant and outcomes after transplantation, including 30-day mortality, median survival time and incidence of cerebrovascular accidents were not significantly impacted upon by bacteraemia. CONCLUSIONS: Bacteraemia is common in VAD patients. However, the incidence of VAD-associated bacteraemia is independent of device type and with aggressive antimicrobial therapy; clinical outcomes need not be affected by the bacteraemia.

Phrenic nerve injury during cardiac surgery: mechanisms, management and prevention.

Phrenic nerve injury is a well-recognised complication of cardiac surgery that can lead to disabling effects from diaphragmatic dysfunction, especially in children and patients with a history of chronic obstructive airway disease. Various mechanisms of injury have been recognised including hypothermia, mechanical trauma and possibly ischaemia. A clear understanding of these mechanisms is important in order to modify surgical techniques to prevent this serious complication of cardiac surgery.

Prophylaxis against atrial fibrillation after cardiac surgery: beneficial effect of perioperative metoprolol.

INTRODUCTION: Multiple agents have been investigated to prevent atrial fibrillation (AF) after cardiac surgery. Several studies have investigated the use of ß-blockers such as metoprolol or amiodarone with promising results. We aimed to investigate perioperative pharmacologic prophylaxis against AF using metoprolol, and amiodarone in combination with metoprolol. METHODS: We conducted a prospective, randomised, single-blind, controlled pilot study in patients undergoing elective cardiac surgery. Subjects were randomised pre-operatively to one of three treatment groups: standard therapy (control) or metoprolol (5 mg IV over 5 min on commencement of bypass then 5 mg IV qid for 24h then 25-50 mg tds orally until discharge) or amiodarone (300 mg over 1h starting shortly after the commencement of bypass, then 900 mg over 24h then 400 mg orally tds until discharge) plus metoprolol as above. Patients had ECG monitoring for the occurrence of AF for six days or until discharge. RESULTS: Two hundred and fifteen patients were enrolled. Between-group differences in AF in an intention-to-treat analysis were not significant: control 34% (23-45%), metoprolol 35% (24-46%), combined 22% (12-33%) (p = 0.21). However 87 patients (40%) did not receive the assigned treatment mainly due to side effects, especially bradycardia. The remaining 128 patients were analysed on a per-protocol basis with the overall difference between the three groups bordering on significance: control 34% (23-45%), metoprolol 26% (9-43%), combined 11% (0-23%) (p = 0.06). Logistic regression analysis, correcting for age and gender, was used to separate the individual effects of metoprolol and amiodarone in the presence of metoprolol which showed that compared to control there was a significant effect of metroprolol on AF incidence (O.R. 0.31 (0.10-0.99), p = 0.048) but not of amiodarone (O.R. 0.97 (0.19-5.02), p = 0.97). CONCLUSIONS: (1) Perioperative metoprolol but not amiodarone itself in combination with metoprolol is associated with a significant reduction in postoperative AF. (2) Perioperative administration of metoprolol and combination of metoprolol with amiodarone is associated with a high incidence of side effects, especially bradycardia. (3) Further studies are indicated to confirm these preliminary findings but in the meantime it would not be unreasonable to implement the use of perioperative metoprolol for routine prophylaxis of AF.