Sameh Mobarek

Clinical variables affecting recovery of left atrial mechanical function after cardioversion from atrial fibrillation

OBJECTIVES We sought to evaluate the effect of clinical factors on recovery of atrial function after cardioversion for atrial fibrillation. BACKGROUND Lack of effective mechanical atrial function (EMAF) after cardioversion of atrial fibrillation predisposes to thromboembolic complications and delays improvement in functional capacity. METHODS Fifty-two patients underwent cardioversion (group I, electrical cardioversion, n = 40; group II, pharmacologic or spontaneous cardioversion, n = 12) for atrial fibrillation. Serial transmitral inflow Doppler variables were recorded after cardioversion until EMAF (atrial filling velocity > 0.50 m/s) was seen. Clinical variables (age, duration of atrial fibrillation, left ventricular ejection fraction, left atrial diameter, underlying cardiovascular disease, antiarrhythmic drug therapy and mode of cardioversion) were tested for an association with the outcomes of recovery of atrial function by day 3 and day 7. RESULTS Effective mechanical atrial function recovered in 68% of patients by day 3 and in 76% by day 7 after cardioversion. The mode of cardioversion was significantly associated with recovery of atrial function by day 3 in bivariate and multivariate analyses (odds ratio 0.12, 95% confidence interval 0.01 to 1.0, for electrical cardioversion). None of the variables had an association with recovery of atrial function by day 7. Group I patients took a longer time to recover atrial function than group II patients (p = 0.012). In addition, group I patients had a significantly lower peak atrial filling velocity (mean [+/-SD] 0.39 +/- 0.19 m/s vs. 0.56 +/- 0.16 m/s) and a higher early filling to atrial filling velocity ratio (2.5 +/- 1.2 vs. 1.5 +/- 0.5) after cardioversion. CONCLUSIONS A high proportion of patients recover EMAF within 1 week after cardioversion. Patients who undergo electrical cardioversion display a greater degree and a longer duration of mechanical atrial dysfunction than those who convert pharmacologically or spontaneously.

Mechanical dysfunction of the left atrium and the left atrial appendage following cardioversion of atrial fibrillation and its relation to total electrical energy used for cardioversion

In 39 patients undergoing electrical cardioversion for atrial fibrillation (AF), we examined the effect of total electrical energy used for cardioversion on postcardioversion peak left atrial (LA) rapid filling velocity (A) and the atrial emptying fraction, and recovery of LA effective mechanical atrial function (defined as peak A velocity > or = 0.50 m/s), as assessed by transthoracic echocardiography. In a subset of 27 patients who underwent pre- and postcardioversion transesophageal echocardiography, we assessed the relation between total electrical energy and LA appendage filling and emptying velocities and spontaneous echo contrast. Patients were randomized to receive an initial shock of 1.5 J/kg based on body weight, or 2.5, 3.5, 5 J/kg, or 360 J, followed sequentially by higher shock intensities until sinus rhythm was achieved. Patients were classified into 4 groups based on quartiles of total energy delivered for cardioversion. Conversion to sinus rhythm was associated with a significant decrease in the LA appendage filling velocities (0.42 +/- 0.20 m/s vs 0.29 +/- 0.14 m/s; p = 0.002) and LA appendage emptying velocities (0.40 +/- 0.22 m/s vs 0.29 +/- 0.18 m/s; p = 0.03), but no change in the incidence of spontaneous echo contrast (61% vs 70%, p = 0.08). The 4 groups of patients did not differ with respect to postcardioversion LA appendage filling velocities, LA appendage emptying velocities, incidence of spontaneous echo contrast, or worsening of spontaneous echo contrast. Similarly, the change in LA appendage filling and emptying velocities associated with cardioversion was not different between the groups. Furthermore, postcardioversion peak A velocity and atrial emptying fraction and recovery of effective mechanical atrial function were similar between the 4 groups. These results suggest that in patients undergoing electrical cardioversion for AF, the total electrical energy used for cardioversion has no effect on the mechanical function of the left atrium or LA appendage following cardioversion.

Prognostic Value of Stress Echocardiography in the Evaluation of Atypical Chest Pain Patients Without Known Coronary Artery Disease

Patients with atypical chest pain frequently lack significant coronary artery disease (CAD) and are, therefore, at low risk for future adverse cardiovascular events. We hypothesized that in this group of patients, stress echocardiography could identify those at risk for cardiac events. We retrospectively reviewed (mean follow-up 23.0 +/- 7.2 months) the prognostic value of stress echocardiography for major (cardiac death, myocardial infarction, congestive heart failure, and unstable angina) and total (major events plus coronary revascularization) cardiac events in 661 patients with atypical chest pain, normal global left ventricular (LV) systolic function, and no history of CAD. A positive stress echocardiogram was defined as the development of new or worsening wall motion abnormalities with exercise stress (80%) or dobutamine (20%). A total of 41 cardiac and 16 major events were noted. The event-free survival for total cardiac events was 97% for a normal stress echocardiogram and 93% for a normal stress electrocardiogram (ECG) at 30 months. A positive stress ECG predicted an event-free rate of 86% compared with 74% for stress-induced wall motion abnormalities and 42% if stress-induced LV dysfunction accompanied the wall motion abnormalities. A strategy recommending invasive studies based on positive stress echocardiogram results increased the per-patient cost, but led to greater savings per cardiac event predicted and provided incremental prognostic value for future cardiac events beyond clinical and stress electrocardiographic data. Thus, stress echocardiography in low-risk patients for CAD appears to be more cost effective than a stress ECG.

Myocardial contrast echocardiography in human beings : Correlation of resting perfusion defects to sestamibi single photon emission computed tomography

The presence of myocardial perfusion abnormalities is generally accepted to suggest underlying coronary artery disease. In previous animal studies, myocardial contrast echocardiography (MCE) has been shown to be useful in delineating areas at risk after coronary occlusions. We sought to compare the presence or absence, size, and location of perfusion defects detected in human beings by MCE and sestamibi single photon emission computed tomography (SPECT). Regional wall motion was qualitatively assessed in the parasternal and apical views of a resting two-dimensional echocardiogram. Coronary angiography was performed in all patients and myocardial contrast echocardiography performed with 2 ml of intracoronary sonicated meglumine (Nycomed). A cine loop of the digitized contrast echocardiograms was used to analyze perfusion defects. Gated SPECT resting images in standard views were obtained after technetium 99m sestamibi (20 mCi) was administered. Visually perceived perfusion defects were established at 30% of maximal counts at end diastole. Perfusion defects by both techniques were planimetered, assigned to one of three perfusion artery territories, and expressed as a percentage of the perfusion territory studied. Comparison was made by linear regression analysis. Forty-one patients were studied. Perfusion defects were observed in 12 (29%) patients by MCE, 19 (46%) patients by SPECT, and 11 (27%) patients by both techniques. No perfusion defects were detected by MCE in 29 (70%) patients, by SPECT in 22 (53%) patients, or by either technique in 21 (51%) patients. The two techniques agreed in 78% of the patients. In 67 matching orthogonal views suitable for comparison between the two techniques, an 82% concordance for the presence or absence of defects was observed. The location of the defects matched in 86% of the cases. A significant correlation (p < 0.001; r = 0.62) between these techniques was observed in assessing the size of perfusion defects. In conclusion, our results suggest that MCE and sestamibi SPECT are comparable techniques for detecting severely underperfused myocardium in human beings.

Is a Full Digital Echocardiography Laboratory Feasible for Routine Daily Use

To determine the feasibility and accuracy of digital echocardiography for routine interpretation of two‐dimensional and Doppler echocardiography, we studied 93 consecutive patients chosen at random from our daily workload. The parameters studied included cavity sizes, biventricular regional and global systolic and diastolic function, valvular structure and function, and presence or absence of pericardial disease. The results were first interpreted using quad screen, digital format cine loops. These results were then compared with the results obtained from reviewing the video‐tape images. Seventy‐nine patients (87%) showed complete concordance between the digital system and video tape. Among the 1156 echocardiographic parameters/measurements examined in all patients, a 99% concordance rate (normal vs abnormal) was found. Disagreements between the digital system and video tape in the patients undergoing two‐dimensional/Doppler exams included mitral valve prolapse in 3, mild valvular insufficiency in 5, a small pleural effusion in 2, and a wall‐motion abnormality in 3 patients. In conclusion, the use of digital technology for evaluation of routine echocardiograms appears to compare favorably with the interpretation of images using the conventional video tape.

Identification of Perfusion Abnormalities Using FSO69, a Novel Contrast Agent, in Conscious Dogs

Recent advances in the production of echocardiographic contrast agents has resulted in the ability to delineate areas of hypoperfusion after coronary occlusions and stenoses following their intravenous injection. Most of these studies though have been done in open chest animals. This study was done to determine if we could assess myocardial perfusion following the intravenous administration of FSO69, a suspension of perfluoropropane filled albumin microspheres (3.6 μm average microbubble size, concentration 8 × 108), in spontaneously breathing closed chest dogs. Twenty‐seven mongrel dogs were instrumented on day 1. The chest was then closed and the dogs were restudied 3–7 days later, while spontaneously breathing. Homogeneous perfusion was observed in most dogs by all three independent and blinded observers. Perfusion abnormalities were likewise identified in most instances by all blinded reviewers on interventions designed to decrease regional blood flow. A good correlation between perfusion defect size between investigators was observed. In summary, our data suggest that FSO69 can be used to assess regional myocardial perfusion in spontaneously breathing dogs. These results support its use in humans.

Assessment of Renal Perfusion in a Canine Model Using FS069, A New Transpulmonary Echocontrast Agent

We have previously demonstrated the safety and efficacy of FS069, a new transpulmonary echocontrast agent, for myocardial opacification. To our knowledge, no information exists regarding the use of this agent for transcutaneous assessment of renal perfusion. We studied 14 mongrel dogs using intravenously administered FS069. Renal ultrasound imaging was performed with a Hewlett‐Packard Sonos 1500 using a 3.5‐MHz transducer. Renal blood flow (ReBF) was altered using renal artery occlusion in four dogs and dipyridamole (0.56 rag / kg IV) in ten dogs. Renal perfusion was quantitatively assessed before and after each intervention using background subtracted peak intensity. ReBF was assessed with radiolabeled microspheres in ten dogs. Renal opacification was observed in all 14 dogs at baseline. The intravenous contrast dose required to produce optimal renal opacification ranged from 0.3–0.7 cc. After renal artery occlusion, peak intensity was reduced from 5.4 ± 5.8 to 0.93 ± 1.1 units (r = 0.99, P < 0.008). As expected, blood pressure and ReBF dropped in all ten dogs after dipyridamole administration. Interestingly, peak intensity increased in all but one dog. An inverse correlation (r = ‐0.75, P = 0.02) was observed between ReBF and peak intensity (percent change from baseline). The inverse relation between ReBF and peak intensity observed suggests vasocon‐striction of the afferent arterioles in response to dipyridamole and a reduced clearance of the contrast. These findings are in agreement with previous data demonstrating decreased renal thallium clearance postdipyridamole administration. Our data document the feasibility to assess renal perfusion under various flow states after intravenous injection of FS069.