Biomedical subjects
Publications and source records attributed to Naeem Merchant.
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Infective endocarditis involving transvenous pacing leads is an uncommon but potentially lethal complication of implantable cardioverter-defibrillator (ICD) implantation. Complete removal of the device and the leads is presently considered to be the optimal treatment in such patients and laser-assisted lead removal is an effective and safe nonthoracotomy approach. However, large vegetations (>10 mm) attached to the lead limit nonthoracotomy explantation because of the potential for hemodynamically embarrassing pulmonary embolization. Laser extraction of leads with vegetation area >300 mm2 has rarely been reported. In this case report, we describe a patient with an infected ICD lead with vegetation greater than 41 x 12.5 mm (512 mm2) in size that was explanted with laser-assistance. The resulting pulmonary embolus produced a 33 x 20 mm pulmonary infarction without hemodynamic or respiratory compromise.
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PURPOSE: To assess the usefulness of cardiac magnetic resonance (MR) imaging for differentiation of true from false left ventricular aneurysm in patients after myocardial infarction. MATERIALS AND METHODS: Cardiac MR images obtained in 22 sequential patients (20 men, two women; mean age, 63 years; age range, 45-75 years) with pathologically proved left ventricular true aneurysm (n = 18) or false aneurysm (n = 4) after myocardial infarction were retrospectively analyzed. The MR imaging protocol included steady-state cine imaging followed by perfusion measurement and delayed contrast-enhanced imaging with delays of 15 and 20 minutes. Differences between true and false aneurysms with regard to maximal internal width of orifice, maximal parallel internal diameter, ratio of maximal orifice to maximal internal diameter, presence of mural thrombus and delayed enhancement of pericardium, left ventricular end-diastolic volume, and left ventricular ejection fraction were analyzed by using the Mann-Whitney U test or Fisher exact test, as appropriate. RESULTS: Inferior wall location was noted in two of four patients with false aneurysm and in none of 18 patients with true aneurysm (P = .03). The remaining aneurysms were apicoanterior (two false, 10 true) or apical (eight true). False aneurysms had a ratio of maximal internal width of the orifice to maximal parallel internal diameter that was significantly lower than that of true aneurysms (0.73 vs 1.00, P < .001) and had a significantly higher left ventricular end-diastolic volume (median, 202 vs 136 mL/m(2); P = .001), as well as a nonsignificant tendency toward lower left ventricular ejection fraction (17% vs 28%, P = .15). Mural thrombus was identified in all four patients with false aneurysm and in seven of 18 patients with true aneurysm (P = .09). Delayed enhancement of pericardium was noted in all four patients with false aneurysm and in three of 18 patients with true aneurysm. Resultant sensitivity of MR imaging for the detection of false left ventricular aneurysm was four of four, specificity was 15 of 18, accuracy was 19 of 22, and positive and negative predictive values were four of seven and 15 of 15 patients, respectively. CONCLUSION: Initial experience with a small number of patients suggests that marked delayed enhancement of the pericardium is a characteristic feature of false aneurysm. Study with a larger patient sample is required to further assess this feature.
The timing of pulmonary valve replacement in adult patients with repaired tetralogy of Fallot remains controversial. A magnetic resonance imaging study in 17 adult patients with repaired tetralogy of Fallot reveals a statistically significant decrease in right ventricular (RV) volume (RV end-diastolic volume 163 +/- 34 to 107 +/- 26 ml/m2, p <0.001; RV end-systolic volume 109 +/- 27 to 69 +/- 22 ml/m2, p <0.001) at a mean follow-up of 21 months after pulmonary valve replacement; whereas RV systolic function remained unchanged (mean RV ejection fraction 32 +/- 7% to 34 +/- 10%, p = 0.12). In no patients with a RV end-diastolic volume >170 ml/m2 or a RV end-systolic volume >85 ml/m2 before pulmonary valve replacement were RV volumes "normalized" after surgery.
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BACKGROUND: Assessment of systemic right ventricular (RV) function is a key point in the follow-up of patients with transposition of the great arteries (TGA). Current echocardiographic assessment of RV function is at best an estimate, and cardiac magnetic resonance (CMR) is considered the gold standard. However, this technique is expensive, has limited availability, and requires significant expertise to acquire and interpret the images. The myocardial performance index (MPI) has recently been studied for assessment of pulmonary RV function and shows promise as a simple yet powerful tool for assessing patients with RV dysfunction of various origins. We set out to compare MPI and CMR assessment of systemic RV function in patients with TGA. METHODS AND RESULTS: Data from patients with TGA (11 with congenitally corrected TGA, 18 with surgically corrected TGA) who had CMR within 6 months of their echocardiogram were reviewed. The average systemic RV ejection fraction (RVEF) by CMR was 39.4+/-11.4%, and the systemic RVMPI for this group was 0.56+/-0.21. There was a strong negative correlation between the systemic RVMPI and systemic RVEF by CMR (r=-0.82, P<0.01). The systemic RVEF can be estimated from this formula: RVEF=65%-(45.2xMPI). CONCLUSIONS: MPI can be used in patients with systemic RVs to assess global function and to estimate an EF with good accuracy.
PURPOSE: To compare the image quality of matched-filtered two-dimensional projection magnetic resonance angiography (MRA) and elliptical centric-ordered (EC) three-dimensional MRA. MATERIALS AND METHODS: Signal-to-noise ratios (SNRs) of matched-filtered two-dimensional projection and EC three-dimensional MRA are developed theoretically and compared by clinical studies, in which 10-20 mL of gadolinium (Gd) was injected at 1.5 mL/second. The artery-vein contrast in two-dimensional projection MRA was managed by manually selecting specific templates for the matched filters. RESULTS: The SNR of matched-filtered two-dimensional projection MRA is superior to that of EC three-dimensional MRA for vessels wider than one pixel due to the integral effect. The artery-vein contrast can be managed flexibly in two-dimensional projection MRA by choosing different templates for the matched filter, while the artery-vein contrast in EC three-dimensional MRA is solely determined by the timing to start the acquisition. CONCLUSION: Matched-filtered two-dimensional projection MRA provides comparable image quality and is a flexible alternative to EC three-dimensional MRA in applications where contrast timing is difficult and temporal information is of interest.
OBJECTIVES: In patients with coronary disease and poor left ventricular function, ventricular reconstruction with revascularization is a surgical option. Details of patient selection and optimal surgical technique are still debated. This study reports results achieved with ventricular reconstruction in 285 patients who had akinesia or dyskinesia associated with relative wall thinning. METHODS: Data were prospectively collected. Reconstruction on the beating heart was accomplished by a modified linear closure plus septoplasty, when indicated, (dyskinetic septum). Preoperatively, 237 (83%) were in symptom class III or IV with congestive heart failure (n =174; 61%), angina (n = 157; 55%), or ventricular tachycardia (n = 107; 38%). Average ejection fraction was 24% +/- 11%, and 144 (51%) had preoperative grade 2+ mitral regurgitation. Operative procedures included coronary artery bypass grafting in 262 (92%), septoplasty in 64 (22%), ablation of ventricular tachycardia in 118 (41%), and a mitral valve procedure in 6 (2%). RESULTS: Operating room mortality was 2.8%. Perioperative support included intra-aortic balloon pumping in 49 (17%) and inotropic drugs in 154 (54%). During a mean follow-up of 63 +/- 48 months, 8 patients required transplantation (interval of 49 +/- 41 months), 2 needed mitral valve replacement, and 9 required use of an implantable cardioverter-defibrillator for ventricular tachycardia. At 1, 5, and 10 years actuarial survivals were 92%, 82%, and 62%. Freedom from sudden death was 99%, 97%, and 94%. Among survivors, symptom class improved in 140 of 208 patients (67%), mean improvement 1.3 +/- 1.1 functional class per patient. Average increase in ejection fraction postoperatively was 10% +/- 9%. CONCLUSIONS: Using wall thinning as a criterion for patient selection, left ventricular reconstruction can be performed with low operative mortality, provides good control of symptoms, excellent long-term survival, and freedom from sudden death. This approach should be considered in all patients with coronary disease, poor left ventricular function, and relative wall thinning.
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Left ventricular surgical reconstruction has been advocated for patients with coronary artery disease, prior myocardial infarction, and poor left ventricular function. The objective of the approach is to resect or exclude all akinetic or dyskinetic nonfunctioning portions of the ventricular cavity and to restore the left ventricle size and shape toward normal as much as possible. We review the pathophysiology of ischemic cardiomyopathy and suggest guidelines for preoperative assessment and patient selection for ventricular reconstruction. Because of the prevalence and prognostic significance of ventricular arrhythmias in this patient population we include in our operative approach a visually directed ablation procedure in those with significant septal scarring. We describe our operative technique and review results achieved with this approach. The procedure results in a significant decrease in ventricular volume, increase in ejection fraction and improvement in apical geometry. We conclude that in selected patients with ischemic cardiomyopathy, left ventricular reconstruction can be accomplished with low operative mortality and results in significant improvement in left ventricular function. During follow up symptom class is decreased in most patients and overall survival at 5 years is 84% and freedom from sudden death is 96%. Ventricular reconstruction should be considered in all patients with coronary artery disease and akinetic or dyskinetic scar.
Pulmonary regurgitation (PR) is associated with adverse outcomes late after tetralogy of Fallot repair. Accurate assessment of PR in these patients is, therefore, fundamental to their clinical treatment; however, accurate ultrasound markers of severity are as yet poorly defined. This is a prospective study of 34 adult patients with repaired tetralogy of Fallot. Cardiac magnetic resonance imaging was used to assess the PR fraction and its hemodynamic significance on the right ventricular volumes. Regurgitant fractions >/= 20% were associated with significant increases in right ventricular end-diastolic volumes. Echocardiographic continuous wave Doppler profiles of the PR jet were used to calculate pressure half-time. Pulmonary pressure half-time < 100 milliseconds was found to be a good indicator of hemodynamically significant regurgitation. This measure is highly reproducible and easily accessible.
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Variable-density (VD) spiral k-space acquisitions are used to acquire high-resolution (0.78 mm), motion-compensated images of the coronary arteries. Unlike conventional methods, information for motion compensation is obtained directly from the coronary anatomy itself. Specifically, periods of minimal coronary distortion are identified by applying the correlation coefficient template matching algorithm to real-time images generated from the inner, high-density portions of the VD spirals. Combining the data associated with these images together, high-resolution, motion-compensated coronary images are generated. Because coronary motion is visualized directly, the need for cardiac-triggering, breath-holding, and navigator echoes is eliminated. The motion compensation capability of the technique is determined by the inner-spiral spatial and temporal resolution. Results indicate that the best performance is achieved using inner-spiral images with high spatial resolution (1.6-2.9 mm), even though temporal resolution (four to six independent frames per second) suffers as a result. Image quality within the template region in healthy volunteers was found to be comparable to that achieved with cardiac-triggered breath-hold scans, although extended acquisition times of around 5 min were needed to overcome reduced SNR efficiency.
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