Aortic wall tension as a predictive factor for abdominal aortic aneurysm rupture: improving the selection of patients for abdominal aortic aneurysm repair.

Aortic wall tension was determined in 40 patients to assess its predictive value in abdominal aortic aneurysm (AAA) rupture. A 3-year retrospective analysis of 243 patients with ruptured AAAs and 45 patients with intact AAAs was conducted. The 288 patient sample was limited to the 40 patients with an abdominal CT scan investigation. Aortic wall tension was calculated using blood pressure data and measurements from computerized tomographic (CT) images of 26 patients with intact AAAs and 14 patients with ruptured AAAs in accordance with LaPlace's Law for wall tension: P x R/W, where P = mean arterial pressure (MAP), R = radius of the vessel, and W = wall thickness of the vessel. The wall tension was approximated with the more readily accessible patient parameters of AAA diameter, MAP, height, and weight. This approximation was termed the body mass index (BMI)-pressure approximation for tension (BPAT), which is AAA diameter/BMI x MAP. Data were analyzed using one-sided t-tests, chi-squared tests, and a regression analysis for the relationship between aortic wall tension and the BPAT. AAA wall tension is a significant predictor of pending rupture. BPAT used to approximate the actual tension in the AAA wall is a more sensitive predictor of rupture than aneurysm diameter alone. A prospective study has been initiated to validate these conclusions.

Exercise prescription for patients with pacemakers.

When developing an exercise program for pacemaker patients, basic information about the pacemaker must be understood. Atrial, ventricular, and dual-chamber devices can produce varying exercise responses and impact the exercise prescription. The type of rate adaptive sensor the pacemaker has will affect the nature of heart rate response, and therefore, must be taken into account when prescribing exercise. While rate modulation is used with most chronotropically incompetent patients, individuals with VVI pacemakers will also benefit from regular exercise. Although the value of exercise testing pacemaker-dependent patients for ECG interpretation may be limited, it is useful in determining exercise capacity and ensuring proper pacemaker function. Participation in a supervised exercise training program can greatly enhance the follow-up and management of pacemaker-dependent patients as well as afford them the opportunity to experience the physical and psychologic benefits typically associated with cardiac rehabilitation.

Medtronic mosaic porcine bioprosthesis satisfactory early clinical performance.

BACKGROUND: The Medtronic (Minneapolis, MN) Mosaic porcine bioprosthesis is an investigational prosthesis which incorporates zero-pressure fixation, aortic root predilation, low profile stent, and alpha oleic acid antimineralization treatment. METHODS: From September 1994 to August 1996, 289 patients (mean age 70 years, range, 28 to 88 years) had 227 (78.5%) aortic valve replacements and 62 (21.5%) mitral valve replacements. Concomitant procedures were performed in 61.2% (139) of aortic valve replacements and 54.8% (34) of mitral valve replacements. Of the aortic valve replacement group 70 (30.8%) were in the 61 to 70 age group and 134 (59.0%) were 71 years or older. Of the mitral valve replacements, 23 (37.1%) were 61 to 70 years and 30 (48.4%) 71 years or older. RESULTS: The early mortality, overall, was 4.2% (12 of 289); for aortic valve replacement it was 4.0% (9) and for mitral valve replacement it was 4.8% (3). The late mortality for aortic valve replacement was 2.6% per patient-year (3 events, 1.3% of total) and for mitral valve replacement it was 3.3% per patient-year (one event, 1.6% of total). The reoperative rate for aortic valve replacement was 3.0% per patient-year (4), while there were no mitral valve replacement reoperations. The freedom from major thromboembolism was 97.3%+/-1.6% for aortic valve replacement and 94.7%+/-3.0% for mitral valve replacement at 1 to 1.5 years. The freedom from reoperation was 96.7%+/-1.7% for aortic valve replacement; there was no reoperation for mitral valve replacement. There were no cases of structural valve deterioration. In the aortic position the mean systolic gradient was low, approximately 11 mm Hg, across all sizes (range 8 to 12 mm Hg at 3 months and 10 to 13 mm Hg at 12 months). In the mitral position the mean diastolic gradient was approximately 5 mm Hg (range, 2 to 6 mm Hg) for all sizes 25 to 31 mm at the early and 1 year follow-up echocardiographic assessment. CONCLUSIONS: The early clinical performance and in vivo hemodynamics are encouraging.

Atenolol for the prevention of arrhythmias following coronary artery bypass grafting.

Seventy patients undergoing aortocoronary bypass grafting were randomized, double-blind, to receive either atenolol or placebo. There were 35 patients in each group. Patients received either atenolol 5 mg intravenously or matching placebo within 3 h of the completion of surgery. A second intravenous dose was administered 24 h following the first and then atenolol 50 mg orally or matching placebo was given for six days. Continuous Holter monitor recordings were obtained for the 24 h immediately preoperatively and continuously for eight days postoperatively. No patient received any antiarrhythmic drug preoperatively. Patients who required pharmacological intervention for the management of postoperative arrhythmias were withdrawn as treatment failures. Holter monitor analysis continued for 24 h following withdrawal of a treatment failure. All patients were analyzed according to the intention-to-treat principle. Both groups were comparable with respect to age, sex, severity of coronary artery disease, left ventricular ejection fraction, preoperative use of beta-blockers, bypass time, aortic cross-clamp time, number of grafts per patient and frequency of preoperative arrhythmias. Arrhythmia analysis was done manually. Supraventricular arrhythmias (atrial tachycardia, atrial fibrillation and atrial flutter) were classified as either mild (less than 0.5 mins, less than 140 beats/min), moderate (0.5 to 30 mins, 140 to 180 beats/min), or severe (longer than 30 mins, more than 180 beats/min). Ventricular arrhythmia analysis was performed with respect to isolated PVCs, couplets, triplets and episodes of nonsustained ventricular tachycardia.(ABSTRACT TRUNCATED AT 250 WORDS)

Elective aortocoronary bypass grafting in the elderly.

Operative mortality, postoperative morbidity and follow up data were analyzed retrospectively from 122 consecutive patients, over 65 years old undergoing elective aortocoronary bypass grafting for symptomatic relief of angina pectoris at the Plains Health Centre, Regina, Saskatchewan, from January 1980 to December 1985. There were two in-hospital deaths (operative mortality 1.6%). Definite perioperative myocardial infarction occurred in 12 patients (9.8%). The 120 survivors were followed for a mean of 32 months. There were three deaths during follow-up, giving a five-year probability of survival of 93%. Twenty-three clinical events (including deaths) occurred during follow-up, giving a five-year probability of event free survival of 72%. Ninety percent of patients say they are pleased with their operation. Seventy-eight percent are currently angina free. These data illustrate the effectiveness of aortocoronary bypass grafting in low risk elderly patients with symptomatic coronary artery disease.

Posterior dislocation of the clavicle causing fatal tracheoesophageal fistula.

A 24-year-old man severely injured in a motor vehicle accident was found to have, on the right side, a pneumothorax, extrapleural hematoma, acromioclavicular dislocation and fracture of the first three ribs and of the transverse processes of C7 and T1. Through a right thoracotomy, transection of the right main stem bronchus and a laceration of the left main stem bronchus were discovered. These were repaired. Twenty days after admission, posterior dislocation of the clavicle at the sternum was noted. A diagnosis of tracheoesophageal fistula was made on the 32nd day but the symptoms had been sternoclavicular and acromioclavicular dislocations. At autopsy the medial end of the clavicle was found to be torn from its articular discand and locked behind the manubrium. The fistula was behind the posterior capsule between the carina and esophagus. The authors conclude that continued pressure from the displaced clavicle may have led to delayed necrosis of the esophagus and that reduction of the dislocated clavicle might have saved the patient's life.