Biomedical subjects
Publications and source records attributed to M Kamalesh.
The acute effect of failed attempts of cardioversion on left atrial (LA) and left atrial appendage (LAA) functions are generally considered benign and no adverse effects have been reported. We report on a subject who had rapid formation of a fresh, mobile thrombus in the LAA despite unsuccessful cardioversion and therapeutic anticoagulation.
Recently published reviews have called into question the sensitvity of transthoracic stress echocardiography to predict cardiac events, especially when the test is negative, compared with myocardial perfusion imaging studies. To our knowledge there are a lack of data assessing the prognostic value of transesophageal echocardiography-dobutamine stress echocardiography (TEE-DSE) in predicting cardiac events. Because TEE-DSE has been reported to be highly accurate for detecting ischemia in patients with suspected coronary artery disease, we tested the hypothesis that a negative TEE-DSE can identify a low-risk group in a population with a high likelihood of coronary artery disease. Between October 1996 and December 1997, 46 high-risk patients with negative TEE-DSE were identified. Annualized pretest risk for all cardiac events using the Framingham model was 4% based on risk factors. Mean age was 64 years. Mean follow-up time was 16.2 months. There were no cardiac deaths. There were 6 soft and 1 hard cardiac event. The annualized combined ischemic cardiac event rate was 3.8%, and for hard cardiac events it was 1.1%. By Kaplan-Meier analysis, 97% of the population remained free of any ischemic event at the end of 1 year and 93% were free at 22 months. We conclude that optimal image quality and enhanced endocardial definition for assessing wall motion changes with TEE translates into better prognostication and approaches that of myocardial perfusion imaging for negative studies. Advances in ultrasound medicine such as contrast enhancement of myocardial definition, which improve diagnostic accuracy of DSE, should translate into better prognostication.
Native valve endocarditis due to Staphylococcus capitis is uncommon and is usually managed conservatively with good outcome. Of the nine previously reported cases there has been only one mortality. We report a case of native aortic valve endocarditis due to S capitis in an elderly diabetic that had a fatal outcome despite appropriate therapy with antibiotics. A review the literature is also presented.
Atrial fibrillation (AF) leads to remodeling of the left atrium (LA) and left atrial appendage (LAA), resulting in atrial myopathy. Reduced LA and LAA function in chronic AF leads to thrombus formation and spontaneous echo contrast (SEC). The effect of inotropic stimulation on LAA function in patients with chronic AF is unknown. LAA emptying velocity (LAAEV) and maximal LAA area at baseline and after dobutamine were measured by transesophageal echocardiography in 14 subjects in normal sinus rhythm (NSR) and 6 subjects in AF. SEC in the LA was assessed before and after dobutamine. LAAEV increased significantly in both groups. However, the LAAEV at peak dobutamine in patients with AF remained significantly lower than the baseline LAAEV in patients who were in NSR (P = 0.009). Maximal LAA area decreased significantly with dobutamine in both groups, but LAA area at peak dose of dobutamine in patients with AF remained greater than baseline area in those in NSR (P = 0.01). Despite the increase in LAAEV, SEC improved in only two of five patients. We conclude that during AF, the LAA responds to inotropic stimulation with only a modest improvement in function.
The circadian rhythm of heart rate variability is present in normal subjects and in patients with angina, with the greatest variation in the normal population and a smaller but significant variation in the anginal group. With beta-adrenergic blockade, significant improvement occurs in all daytime time domain parameters, nocturnal percentage of RR intervals with >50-ms variation, and square root of mean-squared differences of successive RR intervals, daytime total power, and high-frequency band, representing significant improvement in parasympathetic function.
Recently, attention has been focused on transesophageal echocardiographic detection of left atrial appendage function to assess of risk of thrombus formation because of potential benefit of anticoagulation therapy. However, most of these studies have been conducted in patients with atrial fibrillation or mitral valve disease. In this article we review cases of 2 patients without valvular disease who had embolic stroke in sinus rhythm. Transesophageal echocardiography revealed thrombi in the left atrial appendage in both patients. The left atrial appendage function in these patients was compared with that in patients with chronic atrial fibrillation and a control group in sinus rhythm. Left atrial appendage function in the patients with stroke and sinus rhythm was significantly lower than that of patients in the control group in sinus rhythm (P < .001) and was similar to the appendage function in patients with chronic atrial fibrillation. These observations provide further evidence that the finding of reduced left atrial appendage function can be a cause of stroke in patients with sinus rhythm even in the absence of mitral valve disease. Reduced left atrial appendage function may identify patients with unexplained stroke who should receive anticoagulation therapy even in the absence of detectable appendage thrombi.
The angiographic, echocardiographic, and electrocardiographic correlates of ST-segment elevation during high-dose dobutamine-atropine stress were prospectively looked at in a group of high-risk patients. Unlike exercise-induced ST elevation, ST-segment elevation with dobutamine-atropine stress, while indicating transmural ischemia, did not increase rate of arrhythmias and hence by itself may not be an indication to terminate the test.
RATIONALE AND OBJECTIVES: This study evaluated the value of dynamically enhanced fast low-angle shot (FLASH) magnetic resonance (MR) imaging in measuring cardiac output with and without dipyridamole pharmacological stress. METHODS: Ten subjects underwent rest and stress MR imaging. Rest images were acquired using electrocardiogram gated MR (turbo-FLASH: repetition time = 6 mseconds; echo time = 12 mseconds; flip angle = 12 degrees, inversion time = 100) 10 to 45 seconds after intravenous bolus of 0.04 mmol/kg gadolinium (Gd)-DTPA using a Siemens 1.0-tesla Magnetom SP. Stress was induced within the MR imaging scanner with 0.56 mg/kg dipyridamole over 4 minutes with stress MR images obtained after a second bolus of Gd-DTPA in exactly the same position and time intervals. Cardiac output was calculated with a least squares error analysis before and after dipyridamole stress for the left and right ventricles in all 10 patients, and comparison was made with cardiac output by Fick dilution technique during cardiac catheterization in seven patients. RESULTS: This MR analysis methodology shows reasonable correlation (r = 0.953) between left ventricular and right ventricular cardiac output with no effect on cardiac output during immediate dipyridamole stress. Fick dilution studies demonstrated a correlation of 0.96. CONCLUSIONS: Turbo-FLASH MR can demonstrate time-activity curves and cardiac output calculations consistent with theoretical predictions.
Decreased heart rate variability, which may be due to increased sympathetic and decreased parasympathetic activity, has been shown to be predictor of cardiac events after acute myocardial infarction. The present study was undertaken to analyze the effect of beta adrenergic blockade on cardiac autonomic system in patients with chronic stable angina. Nineteen patients (15 males and 4 females, age range 44-74 years) with chronic stable angina were enrolled. After stopping all cardiac medications, patients had two baseline treadmill tests with both reproducible angina and ST depression and a baseline 48-hour ambulatory ECG recording. A long-acting beta-blocker (atenolol or betaxolol) was started and titrated to the maximal tolerated dose. After 1-2 months, a repeat 48-hour ambulatory ECG recording on beta-blocker therapy was obtained. Heart rate variability analysis was performed on the baseline and drug therapy ECG recordings. The average heart rate significantly decreased (P < 0.008), and the mean RR interval significantly increased (P < 0.0001). In the time-domain analysis, the standard deviation, variance, ASDNN5, and SDANN5 were not significantly affected, although the PNN50 increased. In the frequency domain, the total power (P < 0.0001) and the low frequency (P < 0.001) components decreased, while the high frequency spectrum was unchanged. Thus, sympathetic activity significantly declined in patients with chronic stable angina on beta-blocker therapy, while parasympathetic tone demonstrated a heterogenous response.
Localized pericardial effusion leading to cardiac tamponade is seen occasionally in patients after cardiac surgery. This condition may be difficult to diagnose clinically because of unusual presenting symptoms and absence of conventional signs of cardiac tamponade. A case of localized pericardial effusion with presenting symptoms of fever and increasing fatigue is described in this study. The definitive diagnosis was made using transesophageal echocardiography. Surgical drainage of localized effusion resulted in prompt hemodynamic and symptomatic improvement.
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Before heart rate variability (HRV) can be used to investigate the effects of drugs or other clinical interventions in chronic stable angina, it is important to establish the stability and reproducibility of HRV indices over time. HRV analysis was performed on two consecutive 24-hour ambulatory ECG recordings in 19 patients with chronic stable angina. Time-domain analysis included average heart rate, variance, SDNN, SDANN5, ASDNN5 and PNN50. The power spectral analysis was computed using fast Fourier transformation for the total power (0.003 and 0.40 Hz), low frequency (0.04-0.15 Hz), and high frequency (0.15-0.40 Hz) bands. No statistically significant differences in the time or frequency domains were found between the two ambulatory ECG recordings. HRV indices in the time and frequency domains are consistent and reproducible in patients with chronic stable angina. Thus, cardiac autonomic tone can be evaluated using HRV analyses, and any significant changes that occur after medical therapy or other clinical interventions can be ascribed to the intervention rather than the lability of cardiac autonomic tone.
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A 32-year-old male with Budd-Chiari syndrome and stenosis of the inferior vena cava presented to the hospital with severe abdominal pain. Two contiguous, 14 mm, overlapping (joined) Palmaz stents were placed across the area of stenosis in the inferior vena cava. The stents later embolized to the left pulmonary artery and were retrieved non-surgically over a Grollman balloon catheter with transesophageal echocardiographic assistance. This case report highlights the advantages and limitations of transesophageal echocardiographic assistance in such a procedure.
OBJECTIVE: Established noninvasive methods for assessing myocardial ischemia have limitations that might be overcome by MR imaging. We investigated MR myocardial perfusion imaging and MR ventriculography, before and after dipyridamole-induced stress, to determine whether the superior spatial and temporal resolution of MR imaging has advantages for the evaluation of myocardial ischemia. SUBJECTS AND METHODS: Eighteen patients with symptoms suggestive of myocardial ischemia were examined by use of MR perfusion imaging and MR cineangiography before and during dipyridamole-induced stress. Multiplanar gradient-echo MR cineangiography and cardiac gated fast low-angle shot (turbo-FLASH) MR imaging during injection of gadopentetate dimeglumine were used. Results were compared with findings from perfusion scintigraphy and coronary arteriography. RESULTS: The accuracy of the combination MR technique for detecting myocardial ischemia was similar to that of scintigraphy. No significant difference was found between the MR technique and scintigraphy for detecting segments of myocardium supplied by stenosed coronary arteries (> 70% reduction in diameter, as determined by coronary arteriography). The sensitivity of the combination MR technique for angiographically detecting significant coronary artery narrowing was 92%, and the specificity was 100%. For scintigraphy, the sensitivity was also 92% and the specificity was 100%. CONCLUSION: Initial results indicate that a combination of stress MR myocardial perfusion imaging and MR ventriculography is feasible and that this technique can detect myocardial ischemia with an accuracy similar to that of scintigraphy. This technique may make more complete noninvasive assessment of myocardial ischemia possible.
During mitral balloon valvuloplasty, transesophageal echocardiography (TEE) has been employed for the accurate placement of the transseptal needle, guide wires, and balloon catheters and to provide an immediate evaluation of the results of the procedure. We describe a case demonstrating that TEE can be used to avoid a left atrial appendage thrombus during the placement of wires and catheters. With TEE guidance, we feel left atrial appendage thrombi are no longer an absolute contraindication to percutaneous mitral valvuloplasty.
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