The role of chronic atrial stretch and atrial fibrillation on posterior left atrial wall conduction.

BACKGROUND: The posterior left atrium (LA) is involved in the initiation and maintenance of atrial fibrillation (AF). OBJECTIVE: The purpose of this study was to compare conduction patterns on the posterior LA in patients with mitral regurgitation (MR), with and without AF. METHODS: Epicardial mapping of the posterior LA was performed in 23 patients undergoing cardiac surgery. Patients were included in one of three groups: Group A-patients in sinus rhythm with normal left ventricular function undergoing coronary artery bypass grafting, Group B-patients in sinus rhythm with MR undergoing mitral valve surgery, or Group C-patients in persistent AF with MR undergoing mitral valve surgery. Conduction patterns, regional conduction velocity, conduction heterogeneity, conduction anisotropy, and complex fractionated atrial electrograms (CFAEs) were assessed. RESULTS: LA diameter was greater in patients in Groups C (57 +/- 4mm) and B (54 +/- 6mm) than in Group A (39 +/- 7 mm, P <0.01). Patients in Group C had a greater number of lines of conduction delay than Groups A and B (2.0 +/- 0.8 vs 1 +/- 0 and 1 +/- 0, P <0.05). The extent of conduction delay and conduction heterogeneity was greater in Group C than in Group B, which was greater than in Group A (P <0.05). The percentage of CFAEs that remained stable during AF was 61% +/- 17%. There was a significant correlation between CFAEs during AF and regions of slow conduction during pacing (R = 0.36, P <0.001). CONCLUSION: Patients with MR, LA enlargement, and AF have more extensive regions of conduction slowing in the posterior LA. Anatomically constant lines of conduction delay in this region lead to circuitous wavefront propagation. During persistent AF, fractionated electrograms in the posterior LA are distributed to regions demonstrating slow conduction, and the majority remain stable over time.

Anatomically determined functional conduction delay in the posterior left atrium relationship to structural heart disease.

OBJECTIVES: This study sought to characterize the conduction properties of the posterior left atrium (PLA) in patients with different forms of structural heart disease undergoing cardiac surgery. BACKGROUND: The PLA plays an important role in the initiation and maintenance of atrial fibrillation. METHODS: This study included 34 patients having elective cardiac surgery. There were 4 groups of patients: normal left ventricular (LV) function (coronary artery bypass grafting [CABG]); severe LV dysfunction (LVF/CABG); severe mitral regurgitation (MR); severe aortic stenosis (AS). Epicardial mapping of the PLA was performed in sinus rhythm and during differential pacing. Activation patterns, regional conduction velocity (CV), conduction heterogeneity, anisotropy, and total plaque activation time (TAT) were assessed. RESULTS: Left atrial size in patients with LVF/CABG (47 +/- 7 mm) and MR (54 +/- 6 mm) was larger than patients with CABG (39 +/- 7 mm) and AS (42 +/- 6 mm; p < 0.05). During pacing, all patients developed a vertical line of conduction delay running between the pulmonary veins. The extent of this conduction delay was greater in patients with LVF/CABG and MR than patients with AS and CABG (p < 0.05). Conduction heterogeneity, anisotropy, and TAT were greater in patients with LVF/CABG and MR than patients with CABG (p < 0.05). These changes resulted in circuitous wave front propagation. CONCLUSIONS: There is a line of functional conduction delay in a consistent anatomical location in the PLA in patients with structural heart disease. This is most marked in conditions associated with significant chronic atrial enlargement and leads to circuitous wave front propagation, suggesting a potential role in arrhythmogenesis.

Patterns of postoperative systemic vascular resistance in a randomized trial of conventional on-pump versus off-pump coronary artery bypass graft surgery.

BACKGROUND: Off-pump coronary artery bypass grafting (OPCAB) is associated with a less intense systemic inflammatory response according to biochemical markers. We studied systemic vascular resistance (SVR) as a physiologic response to systemic inflammatory response to determine any differences between OPCAB and on-pump coronary artery bypass grafting (ONCAB) in a prospective randomized trial. METHODS: One hundred consecutive patients were randomized to OPCAB or ONCAB, 50 in each group. Antifibrinolytics and steroids were not used. All protocols were identical except for cardiopulmonary bypass. Temperature, SVR index, cardiac index, and blood pressure were measured continuously for the first 24 hours postoperatively. All patients were reviewed at 30 days. RESULTS: There was no 30-day mortality, no stroke, and no acute renal failure. Mean temperature peaked at 37.5 degrees C at 12 hours (p = 0.700 between groups). Mean SVR index fell to 1,900 dyne x cm(-5) x m(-2) at 12 to 18 hours; 42% of OPCAB and 32% of ONCAB patients developed very low SVR index (<1,500 dyne x cm(-5) x m(-2)). The incidence of high SVR (>2,500 dyne x cm(-5) x m(-2)) fell from 20% to 2% by 12 to 18 hours. The extent and pattern of SVR index responses were similar in both groups (p = 0.840). Mean cardiac index peaked at 3.0 L x min(-1) x m(-2), 12 to 18 hours postoperatively (p = 0.815 between groups); 84% of OPCAB and 90% of ONCAB had cardiac index greater than 2.2 L x min(-1) x m(-2) at all times. Only 10% of patients required vasopressors. Blood pressure responses were also similar (p = 0.314). CONCLUSIONS: The incidence of low SVR, and patterns of SVR changes were similar in ONCAB and OPCAB, and were clinically unimportant as few patients required vasopressor support. Cardiac outputs and clinical outcomes were excellent in both groups.

Multiple mediastinal metastasis of ovarian carcinoma.

Secondary mediastinal tumours are rare. We present a case report of multiple mediastinal metastasis of ovarian cancer, a very rare occurrence with only two cases previously reported in the literature.

Robotic cardiac surgery at Epworth hospital.

Epworth Hospital is the first in the southern hemisphere to acquire the da Vinci Robot to facilitate minimally invasive cardiac surgery. Applications for this new technology include mitral valve repair, atrial septal defect closure, single coronary artery bypass graft to coronary arteries on the front of the heart, ablative surgery for atrial fibrillation and insertion of epicardial pacemaker electrodes. A team of surgeons from the Epworth Hospital have trained at East Carolina University (ECU) Greenville, North Carolina, USA; including surgeons, anesthetists, perfusionist and nurses. Following this, during a week in March, a proctoring surgeon from the USA, Dr. Wiley Nifong, assisted the Epworth team with their initial seven operations, which all proceeded without incident. The initial operative times were longer than the standard surgery, although with additional experience, now totalling 24 patients in all, these times have shortened considerably. The experience to date is summarized as an Addendum to this manuscript.

The radial artery in coronary surgery: a 5-year experience--clinical and angiographic results.

BACKGROUND: The radial artery (RA) has been used extensively by us as a way of reducing the use of the saphenous vein. It has been hoped that the RA will maintain greater late patency than the saphenous vein. We evaluated our initial 5-year experience with the RA in coronary surgery. METHODS: We studied 6,646 consecutive patients who had a single RA (4,872), or bilateral RA (1,774), as coronary grafts, from June 1995 to June 2000. Angiograms were performed mostly in symptomatic patients, or as part of a research project in asymptomatic patients. RESULTS: The patients' mean age was 65.1 years; 23% had diabetes, 14% had unstable angina, and 42% had prior myocardial infarction. An average of 3.3 grafts per patient were performed, 87% from arterial conduit. Conduits used were RA (8,420), left internal thoracic artery (6,296), and right internal thoracic artery (1,076). Operative mortality occurred in 58 (0.9%) patients, stroke in 92 (1.4%), deep sternal infection in 97 (1.4%), reoperation for hemorrhage in 56 (0.9%), and myocardial infarction in 52 (0.8%). Peak mean postoperative creatine kinase MB (CKMB) was 16.5 IU/L. Two patients developed fingertip ischemia. Postoperative angiographic RA patency was 90.2% (333 of 369 distal anastomoses). CONCLUSIONS: Good early clinical and angiographic results can be achieved by using the RA in coronary surgery.