Jamshid Alaeddini

Structural remodeling of the left atrial appendage in patients with chronic non-valvular atrial fibrillation: Implications for thrombus formation, systemic embolism, and assessment by transesophageal echocardiography.

Left atrial appendage (LAA) is frequently the site of thrombus formation in patients with chronic atrial fibrillation (AF). Transesophageal echocardiography and hematologic studies have identified blood flow stasis (spontaneous echogenic contrast) and abnormal coagulation (increased serum fibrinogen) as important predisposing factors to formation of LAA thrombi. However, the third component of the Virchows triad, i.e., endothelial abnormalities, has not been adequately studied. Accordingly, we studied, at necropsy, the LAA morphology in 46 hearts of patients with (n = 22) and without (n = 24) chronic AF. Compared to patients without AF, those with AF had significantly larger LAA volumes (1.7% 1.1 vs. 5. 4% 3.7 mL, p = 0.0002), and larger luminal surface area of the bisected LAA (4.4% 1.8 vs. 7.1% 4.5 cm(2), p = 0.01). However, both the absolute and relative surface area of the transected pectinate muscles were reduced in patients with AF (2.6% 1.1 vs. 1.8% 1.0 cm(2), p = 0.02 and 38% 15 vs. 21% 14%, p = 0.0003). In addition, in most patients (73%) with chronic AF, the LAA showed significant endocardial thickening with fibrous and elastic tissue (endocardial fibroelastosis) compared to those without AF (13%, p < 0.0001). Endocardial fibroelastosis resulted in a smooth LAA luminal surface and encased the pectinate muscles. These findings suggest that LAA remodeling (dilation, stretching, and reduction in pectinate muscle volume, as well as endocardial fibroelastosis) occurs frequently in chronic AF and may contribute to the increased risk of thrombus formation and systemic embolism. Additionally, the information may have relevance in interpreting transesophageal echocardiographic images of the LAA in patients with chronic AF.

Repeated dual external direct cardioversions using two simultaneous 360-J shocks for refractory atrial fibrillation are safe and effective.

Failure of cardioversion of atrial fibrillation (AF) to sinus rhythm (SR) by standard external direct current cardioversion (DCC) may be due to failure of delivery of enough defibrillating energy rather than to the true refractoriness of AF. Ninety‐nine patients with persistent AF (76 male; age 63.7 ± 0.4 years; weight 113.1 ± 25.1 kg) who failed standard DCC were included in this report. Under anesthesia, QRS synchronous shocks were delivered across anteroposterior electrodes in the following sequence: (1) a single 360‐J shock; (2) another single 360‐J shock within 2 minutes; (3) 30 minutes of rest, reinduction of anesthesia and delivery of two simultaneous monophasic 360‐J shocks. All patients underwent all three DCC steps. Sixty‐six (67%) patients converted to SR following the first dual simultaneous shock. Fourteen patients (14%) required more than one dual shock to achieve SR. This increased the overall success rate of resuming SR to 81%. Except for minor skin burns in three patients there were no procedure related complications. On follow‐up at 1 month, 55 (56%) patients were still in SR, whereas 50 (51%) patients maintained SR at 12 months. This was similar to our general DCC population (55% of the 1698 patients were in SR 6 months post‐DCC, P = ns). In conclusion, dual external monophasic 360‐J DCC is an effective rescue technique for restoration of SR in patients with AF refractory to standard DCC. AF in these patients seems to be as amenable to chronic suppression as AF in the general population of DCC patients.

Comparison of modes of death and cardiac necropsy findings in fatal acute myocardial infarction in men and women >75 years of age

In comparing the cause of death and other cardiac morphologic findings among 60 women and 40 men aged >75 years who died of acute myocardial infarction, we found that women died more often from mechanical complications than left ventricular pump failure. Women had cardiomegaly, nonanterior location of acute myocardial infarction, healed myocardial infarcts, and dilated left ventricular cavity less often than men.

Effect of early administration of atropine on paradoxic sinus deceleration during dobutamine stress echocardiography

Dobutamine stress echocardiography (DSE) is a well-established, safe, and reliable technique for diagnosis of coronary artery disease. The generally accepted protocol for DSE involves infusion of increasing doses of dobutamine from 5 to 40 g/kg/min at 3-minute intervals. In about 1/3 of patients, however, target heart rate cannot be achieved by the administration of dobutamine alone. Failure to achieve an adequate heart rate during DSE is attributed to the use of -adrenergic blocking agents, chronotropic incompetence, or paradoxic sinus deceleration (PSD). PSD is characterized by an initial increase followed by a significant decrease in heart rate during incremental doses of dobutamine. This is believed to result from activation of the cardioinhibitory reflex (Bezold-Jarisch reflex) through left ventricular sensory receptors. Although suggested by some, it is unclear whether left ventricular inferoposterior wall ischemia is the trigger for PSD. In the present study, we sought to identify the characteristics of patients with PSD during DSE and to determine whether early administration of atropine could prevent its development. • • • The study population consisted of 114 consecutive patients (age 36 to 91 years [66 12]; 66 women [58%]) with suspected coronary artery disease who were referred for DSE between March and June 2000. Patients were prospectively randomized into 2 protocols. Group A (n 55) underwent standard DSE protocol, consisting of incremental doses of dobutamine from 5 to 40 g/kg/min at 3-minute intervals, and if needed, up to 1 mg of atropine (0.25 mg doses at 2-minute intervals) at the completion of the 40 g/kg/min dose of dobutamine. A 3-minute infusion of dobutamine at 50 g/kg/min was given if necessary at peak (n 2). Patients in group B (n 59) underwent the same protocol except for administration of atropine at completion of the 10 g/kg/min dose of dobutamine with the aim to increase heart rate by 25% before advancing to the next dose of dobutamine. Atropine was not administered if the patient had a specific contraindication. End points for DSE termination were: (1) attainment of target heart rate, (2) completion of stress protocol, (3) echocardiographic evidence of ischemia, or (4) development of significant arrhythmia, hypertension, hypotension, or intolerable symptoms. A standard echocardiographic image acquisition protocol was used and heart rate was recorded from 12-lead electrocardiograms performed at 1-minute intervals. DSE was considered positive for ischemia if any worsening in left ventricular wall motion developed during the test except for a change from akinesia to dyskinesia. PSD was defined as a reduction in heart rate of 5 beats/min lasting for 3 minutes at dobutamine infusion rates of 10 g/kg/min. Data are presented as mean SD and numbers and percentages. Differences between continuous variables were assessed with the unpaired Student’s t test. Chi-square or Fisher’s exact test compared proportions. No statistically significant differences were noted between the 2 groups with regard to age, sex, baseline heart rate, blood pressure, and left ventricular ejection fraction, as well as risk factors for coronary artery disease (Table 1). Similarly, the number of patients who were on -adrenergic blocking agents was not significantly different in the 2 groups (28 [52%] vs 35 [59%], p NS) (Table 1). An equal proportion of the patients in the 2 groups (73%) reached target heart rate ( 85% predicted maximum heart rate for age). In addition, DSE was terminated in 7 patients (13%) in group A and 6 patients (10%) in group B due to myocardial ischemia (p NS). Coronary angiography was performed within 1 month of DSE in 9 of these 13 patients (5 in group A and 4 in group B) and showed significant coronary artery disease ( 50% luminal narrowing in 1 major epicardial coronary artery) in all patients. Safety considerations were the reasons for termination of DSE in 6 patients (11%) in group A and 2 patients (3%) in group B (p NS). The remaining 2 patients (3%) in group A and 8 patients (14%) in group B did not reach target heart rate despite maximal doses of dobutamine and atropine (if not contraindicated) (p NS). Five of the 8 patients in group B who did not reach target heart rate were taking -adrenergic blocking agents, From the Department of Medicine, Division of Cardiology, Albert Einstein College of Medicine, Bronx, New York. Dr. Shirani’s address is: Jack D. Weiler Hospital of the Albert Einstein College of Medicine, Division of Cardiology, 1825 Eastchester Road, Bronx, New York 10461-2373. E-mail: jshirani@montefiore.org. Manuscript received August 6, 2001; revised manuscript received and accepted October 31, 2001.

Variations in Collagen Content of Asynergic Left Ventricular Segments in Explanted Hearts of Men With Ischemic Cardiomyopathy

Transmural left ventricular (LV) biopsies obtained at the time of coronary artery surgery have been used to evaluate the histomorphologic features of viable myocardium in patients with ischemic cardiomyopathy. 1–16 Usually, 1 or 2 biopsies are obtained from the center of the LV region supplied by the left anterior descending coronary artery. The biopsy specimens (1.2 to 1.5 mm in diameter) are subsequently used for quantifi cation of collagen using grids with visual point counting. 1–16 The degree of myocardial fi brosis in these biopsy samples has been correlated with the results of various noninvasive tests used for assessment of preoperative regional myocardial viability. However, it is unclear whether the data obtained from these transmural biopsy samples would uniformly refl ect the overall histomorphologic features of the entire LV region as evaluated by noninvasive imaging techniques. In this study, we determined the extent of variation in volume fraction of collagen of 2-mm-wide (biopsy-equivalent) consecutive transmural sections of mid-LV anterior wall from explanted hearts of men with chronic ischemic heart disease. Moreover, we examined the variability of fi brosis in normal, ischemic, and scarred myocardium as assessed by thallium. x7fx7fx7f The 13 men with ischemic cardiomyopathy awaiting cardiac transplantation were prospectively enrolled in a study determining the relation of thallium uptake to myocardial fi brosis. 17 Patients’ ages ranged from 41 to 62 years (mean 54). All patients had severe (New York Heart Association functional class III to IV) heart failure and/or angina pectoris and multivessel coronary artery disease, and were listed as stable outpatients at the time of enrollment. Patients with recent acute myocardial infarction or unstable angina were excluded from the study. Cardiac transplantation was performed at a mean of 6 2 months after the nuclear imaging studies. The explanted hearts were fi rst fi xed in formaldehyde. The left ventricle was then sliced transversely at a mean thickness of 8 mm/slice from apex to base. A mid-LV slice was divided into 8 large segments. The 2 large segments representing the anterior wall were then embedded in paraffi n, cut at a thickness of 5 m and stained with picrosirius red. These segments were further divided into consecutive 2-mmwide transmural sections. Percent collagen was then quantifi ed using a computerized image analysis system (Quantimet 520, Cambridge, Massachusetts) in the large segments and in each small section, as previously described. 18 All patients underwent stress-redistribution-reinjection thallium single-photon emission computed tomography. Short-axis tomograms at the mid left ventricle, corresponding to that used for the histomorphologic study, from the 3 sets of thallium images (stress, redistribution, and reinjection) were analyzed objectively, using a semiautomated quantitative circumferential profi le as previously described. 19 Briefl y, for each patient, an operator-defi ned region of interest was drawn around the LV activity of each short-axis slice on the corresponding stress, redistribution, and reinjection images. As with the histologic assessment, the myocardial activity was divided into 8 segments of equal arcs, beginning at the center of the anterior LV wall and proceeding clockwise. Mean counts per pixel within the 2 anterior wall segments (anteroseptal and anterolateral) on stress, redistribution, and reinjection images were computed. The myocardial segment with the highest thallium activity on the stress tomogram was used as the normal reference segment. The same segment in redistribution and reinjection thallium