Manohara P.J. Senaratne

Endothelium-Dependent Relaxation in Aorta of BB Rat

The study was undertaken to determine whether the phenomenon of endothelium-dependent relaxation was impaired in the spontaneously diabetic BB Wistar rat. Endothelium-dependent relaxation in the aorta of overtly diabetic animals was compared with that in nondiabetic BB rats. The relaxative responses were elicited in vitro to acetylcholine (−8.0 to −5.5 log M) and histamine (−7.0 to −3.0 log M) after precontraction with norepinephrine (−6.0 log M). The maximum relaxations produced by both acetylcholine and histamine expressed as percentages of the contractions to norepinephrine were significantly lower in diabetic than in nondiabetic rats. Scanning electron microscopy revealed that in diabetic BB rats there was consistent evidence of swollen cells, raised nuclei, and sloughing of nuclei in endothelial cells of the aorta. In nondiabetic animals these features were not evident. These findings suggest the presence of a functional and morphological defect in endothelial cells in the aorta of the BB rat.

Postpacemaker implant pericarditis: incidence and outcomes with active-fixation leads.

SIVAKUMARAN, S., et al.: Postpacemaker Implant Pericarditis: Incidence and Outcomes with Active Fixation Leads. Pericarditis has been noted as a potential complication of pacemaker implantation. This study evaluated the risk of developing pericarditis following pacemaker implantation with active‐fixation atrial leads. Included were 1,021 consecutive patients (mean age 73.4 ± 0.4 years, range 16–101 years; 45.2% women) undergoing new pacemaker system implantation between 1991 and 1999 who were reviewed for the complication of pericarditis. The incidence and outcomes of postimplantation pericarditis in patients receiving active‐fixation atrial leads were compared to those not receiving these leads. Of 79 patients who received active‐fixation atrial leads, 4 (5%) developed pericarditis postpacemaker implantation. Of 942 patients with passive‐fixation atrial leads or no atrial lead (i.e., a ventricular lead only), none developed pericarditis postoperatively (P < 0.001). Of patients receiving active‐fixation ventricular leads only (n = 97), none developed pericarditis. No complications were apparent at the time of implantation in patients who developed pericarditis. Pleuritic chest pain developed between 1 and 28 hours postoperatively. Three patients had pericardial rubs without clinical or echocardiographic evidence of tamponade. They were treated conservatively with acetylsalicylic acid or ibuprofen and their symptoms resolved without sequelae in 1–8 days. One patient (without pericardial rub) died due to cardiac tamponade on postoperative day 6. Postmortem examination revealed hemorrhagic pericarditis with no gross evidence of lead perforation. Pericarditis complicates pacemaker implantation in significantly more patients who receive active‐fixation atrial leads. It may be precipitated by perforation of the atrial lead screw through the thin atrial wall. Patients developing postoperative pericarditis should be followed closely due to the risk of cardiac tamponade.

Impairment of endothelium‐dependent relaxation: an early marker for atherosclerosis in the rabbit

1 Cholesterol feeding of rabbits impairs the endothelium‐dependent relaxation (EDR) evoked by acetylcholine (ACh) in the aorta. The experiments described in this paper were undertaken to examine the influence of age upon this phenomenon. 2 Rabbits aged 8 weeks and 46 weeks were fed a diet containing 2% cholesterol and other lipids for 4 weeks. Age‐matched control animals were fed a standard rabbit diet. The concentrations of cholesterol and triglycerides in plasma were measured and the extent of atherosclerosis was estimated by staining the aortae with Sudan Red. Light and electron microscopy were undertaken also. 3 Rings of aorta were prepared for recording isometric tension. They were contracted with noradrenaline (NA) and EDR elicited by adding ACh. 4 The young rabbits showed weight gain, hypercholesterolaemia, prominent Sudan Red staining, together with scanning and transmission electron microscopic (SEM and TEM) features of cholesterol‐induced atherosclerosis. The older animals showed significant weight loss and hypercholesterolaemia. The aortae of these animals showed no significant sudanophilia or light microscopic features of atherosclerosis. The SEM appearances were similar to the young animals fed cholesterol. 5 EDR to ACh was significantly impaired in both groups of cholesterol‐fed rabbits. The maximal relaxations to ACh in young control and cholesterol‐fed rabbits were 46.4 ± 2.9% and 24.0 ± 4.3% (mean ± s.e. mean, n = 8, P < 0.05) of the contractile response to NA (1 μmol 1‐1). The corresponding results in the age control and cholesterol‐fed rabbits were 31.8 ± 3.9% and 9.1 ± 1.5% (n = 9, P < 0.05). 6 The young rabbits were far more susceptible to cholesterol‐induced atherosclerosis than older animals and these changes were accompanied by loss of EDR. In the older animals the loss of the latter property was not accompanied by a significant degree of atherosclerosis although hypercholesterolaemia was present.

Absence of effect of calcium antagonists on endothelium-dependent relaxation in rabbit aorta.

1 The effect of chronic feeding of New Zealand White rabbits with nicardipine (60 mg kg−1 daily for 5 weeks) on the endothelium‐dependent relaxation (EDR) to acetylcholine (ACh) was examined in vitro. The effect of acute exposure to nicardipine and diltiazem (10 μmol l−1) in the tissue bath was also examined. 2 A bioassay system for endothelium‐dependent relaxation factor (EDRF) in which a rabbit aortic ring with endothelium removed was used as recipient and a segment of rabbit aorta with endothelium as donor (producing EDRF in response to ACh) was developed. This system enabled the effect of nicardipine on the synthesis/release and on the relaxation to EDRF to be studied separately. 3 The maximum relaxations to ACh in control and nicardipine‐fed animals were 43.6 ± 5.5 and 53.8 ± 6.7% (mean ± s.e.mean) of the contractile response to noradrenaline (NA, 1 μmol l−1) (n = 6, P > 0.05). Similarly the EDR to ACh was not significantly altered by acute exposure (30 min) to nicardipine or diltiazem. The maximum relaxations without and with nicardipine were 32.4 ± 4.2% and 28.0 ± 3.1% of the contraction to NA (1 μmol l−1) (n = 11, P > 0.05). The corresponding data for diltiazem were 42.1 ± 5.7 and 36.4 ± 7.3% respectively (n = 11, P > 0.05). 4 Both calcium antagonists inhibited the contraction induced by potassium (100 mmol l−1). Nicardipine and diltiazem in concentrations of 100 μmol l−1 reduced the potassium‐induced contraction to 33.0 ± 9.0% and 53.8 ± 6.7% of control respectively (n = 6, P < 0.05). 5 In the bioassay experiments the infusion of nicardipine on (a) the recipient tissue only and (b) the donor and the recipient tissue had no significant effect on the relaxant response observed in the recipient tissue when superfused with Krebs‐bicarbonate buffer containing ACh via the donor tissue (n = 6, P > 0.05). 6 These results indicate that nicardipine and diltiazem had no significant effect on synthesis/release and the relaxant response to EDRF in the rabbit aorta. Thus the translocation of Ca2+ accompanying the EDR to ACh in the rabbit aorta is likely to utilize Ca2+ channels not blocked by these calcium antagonists.

Feasibility of direct discharge from the coronary/intermediate care unit after acute myocardial infarction

OBJECTIVES This investigation was designed to determine the feasibility and cost-effectiveness of direct discharge from the coronary/intermediate care unit (CICU) in 497 consecutive patients with an acute myocardial infarction (AMI). BACKGROUND Although patients with an AMI are traditionally treated in the CICU followed by a period on the medical ward, the latter phase can likely be incorporated within the CICU. METHODS All patients were considered for direct discharge from the CICU with appropriate patient education. The 6-week postdischarge course was evaluated using a structured questionnaire by a telephone interview. RESULTS There were 497 patients (men = 353; women = 144; age 63.5 +/- 0.6 years) in the study, with 29 in-hospital deaths and a further 11 deaths occurring within 6 weeks of discharge. The mode length of CICU stay was 4.0 days (mean 5.1 +/- 0.2 days): 1 to 2 (12%), 3 (19%), 4 (21%), 5 (14%), 6 to 7 (19%) and > or = 7 (15%) days, respectively with 87.2% discharged home directly. Of the 425 patients surveyed, 119 (28.0%) indicated that they had made unscheduled return visits (URV) to a hospital or physicians office: 10.6% to an emergency room, 9.4% to a physicians office and 8.0% readmitted to a hospital. Of these URV, only 14.3% occurred within 48 h of discharge. Compared to historical controls, the present management strategy resulted in a cost savings of Cdn.

Pacemaker longevity : Are we getting what we are promised?

4,044.01 per patient. CONCLUSIONS Direct discharge from CICU is a feasible and safe strategy for the majority of patients that results in considerable savings.

Exercise testing after myocardial infarction: Relative values of the low level predischarge and the postdischarge exercise test

Background: Although pacemaker manufacturers provide projections on longevity, these projections cannot be relied upon due to the assumptions of output parameters being far in excess of those programmed in clinical practice.

A 19-year study on pacemaker-related infections: a claim for using postoperative antibiotics.

This study was undertaken to compare the relative values of the low level predischarge exercise test and the postdischarge (6 weeks) symptom-limited test in 518 consecutive patients admitted with an acute myocardial infarction. Of the patients who did not develop significant ST segment depression or angina during the predischarge test, the symptom-limited test also remained negative in 91.5 and 91.9% of the patients, respectively. Similar results were obtained with ST segment elevation and the systolic blood pressure response during the two exercise tests with only 2.1 and 11.4% changing from normal to abnormal, respectively. Discriminant function analysis was done to predict the occurrence of coronary events (unstable angina, reinfarction, cardiac failure, cardiac death) with use of the data from the exercise tests together with other clinical and investigational data. The jackknife method correctly classified 71.9 and 71.4% of the patients with the data from the predischarge exercise test and symptom-limited test, respectively. Combining the data from the two tests improved the overall predictive accuracy to only 75.0%. It is concluded that the routine performance of a symptom-limited test 6 to 8 weeks after infarction does not reveal any significant additional information in those patients who have undergone a predischarge low level exercise test. Thus the 6 to 8 week test should be restricted to selected patients after myocardial infarction.

Outcomes of an ambulatory cardiac pacing program: indications, risks, benefits, and outcomes.

Although the incidence of pacemaker‐related infection (PMINF) is low, it necessitates removal of the pacing system. There is currently no consensus on antibiotics during implantation.

Adequacy of an Exercise Test in Excluding Angina on Patients Presenting to the Emergency Department with Chest Pain

The purpose of this review was to evaluate the economical benefits and outcomes of an ambulatory pacing system implantation program that began in 1991 for new and replacement pacing system implantations. Patient access, incidetice of complications, hospital bed day utilization, economic impact, safety, and practicality of the Ambulatory Pacing System Implantation Program was retrospectively reviewed from August 1991 to March 1994. The Ambulatory Pacing System Implantation Program includes pre‐operative outpatient assessment in the pacemaker clinic, admission to the Day Medical Unit followed by same day pacing system implantation, discharge home after a short period of observation, and, in selected cases, cardiac monitoring, followed by pacemaker clinic visit 24‐hours postimplantation. Results: Two hundred four cardiac pacing systems, 154 new and 50 replacements (pulse generator/leads), were implanted under the guidelines of the Ambulatory Pacing System Implantation Program between August 1991 and March 1994. Eighty‐seven percent of the patients were implanted with passive fixation leads, the remaining with active fixation leads: all but four of which were leads implanted in the atria. Preprocedure wait time was decreased from 16 to 2 days for elective pacing system implantation. The incidence of lead dislodgment in the first, second, and third year of the Ambulatory Pacing System Implantation Program was 20%, 12%, 5%, respectively: compared to 11% for a similar number of cases in previous years done as inpatients. The incidence of new infection was 2.4% compared to < 1% in previous years. Six of the 204 (2%) cases required admission overnight. A total savings of 1,456 bed days (