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Ramesh Hariharan

Publications and source records attributed to Ramesh Hariharan.

5 recordsLinked to original sources
PubMed2003

The analysis of microarray data.

This article describes issues, techniques and algorithms for analyzing data from microarray experiments. Each such experiment generates a large amount of data, only a fraction of which comprises significant differentially expressed genes. The precise identification of these interesting genes is heavily dependent not only on the statistical data analysis techniques used but also on the accuracy of the previous oligonucleotide probe design and image analysis steps as well. Indeed, wrong decisions in these steps can multiply the number of false positives by many-fold, thus necessitating a careful choice of algorithms in all three steps. These steps are described here and placed in the context of commercial and public tools available for the analysis of microarray data.

Data Interpretation, Statistical↗
PubMed2003

Inappropriate shock delivery and biventricular pacing cardiac defibrillators.

In the United States, physicians adapt currently available defibrillators to accommodate leads for biventricular pacing in those congestive heart failure patients who might benefit from cardiac resynchronization and who are additionally at risk for sudden cardiac death. The adaptation of the lead system of available defibrillators to also allow them to function as biventricular pacemakers presents occasions in which inappropriate shocks are delivered due to double counting of the right and left ventricular depolarizations by the implantable cardiac defibrillator. We reviewed a series of inappropriate shock deliveries that occurred after the implantation of biventricular pacing cardiac defibrillators at our institution; all of these shocks were related to ventricular double counting. Each had different underlying causes and management strategies. Complications such as these emphasize the importance of attentiveness to ventricular channel electrograms and to device sensing with the use of biventricular pacing cardiac defibrillators. In addition, a thorough working knowledge of pacemaker and defibrillator operation is essential for the prediction and correction of inappropriate therapies.

Aged↗
PubMed2002

Magnetic resonance imaging of myocardial fibrosis in hypertrophic cardiomyopathy.

Myocardial fibrosis can occur in patients who have hypertrophic cardiomyopathy in the absence of epicardial coronary disease. In such patients, myocardial fibrosis has been linked to a poorer prognosis than in those without fibrosis. Gadolinium-DTPA delayed-enhancement magnetic resonance imaging (de-MRI) accurately identifies regions of myocardial fibrosis. We used de-MRI to screen for myocardial fibrosis in 8 patients with nonobstructive hypertrophic cardiomyopathy that had been diagnosed by 2-dimensional echocardiography. After localization of the heart and acquisition of electrocardiographically gated cine images, gadolinium-DTPA (0.2 mmol/kg) was administered to the patient. Fifteen minutes later, de-MRI images were obtained using a T1-weighted, inversion-recovery fast, low-angle shot sequence. Images were gated to end-diastole and obtained during a single breath-hold. The inversion time was modified iteratively to obtain maximal nulling of the signal from the ventricular myocardium. Regions of myocardium with abnormally high signals (>300% of remote normal myocardium) were designated as fibrotic. Eight patients with hypertrophic cardiomyopathy underwent de-MRI. The mean age was 52 years, the mean left ventricular mass was 201 grams, and the mean ejection fraction was 0.68. In the 6 patients with recent clinical deterioration, de-MRI showed clearly delineated areas of myocardial fibrosis; no such areas were seen in the 2 asymptomatic patients. We conclude that patients with symptomatic hypertrophic cardiomyopathy display regions of abnormal signal intensity on de-MRI that likely represent fibrosis. This technique may provide useful information in the evaluation of such patients and warrants further study.

Adult↗
PubMed2002

Can stent-angioplasty be a valid alternative to surgery when revascularization is indicated for anomalous origination of a coronary artery from the opposite sinus?

When intervention is indicated for anomalous origination of a coronary artery from the opposite sinus, stent-angioplasty may seem more attractive than coronary artery bypass grafting. However, in the case of anomalous origination of a coronary artery from the opposite sinus, the anatomy is quite different from that encountered in atherosclerotic disease, and stent-angioplasty would involve unusual challenges, both in technique and prognostic outcomes. We illustrate these points by presenting the 2 first cases in which intervention was indicated because of severe symptoms. We conclude from this preliminary study that coronary artery bypass grafting should still be considered the preferred (although unproven) method of revascularization in patients who have symptomatic anomalous origination of a coronary artery from the opposite sinus. Until adequate data have been gathered to evaluate the late results of stent-angioplasty in these patients (in comparison with the results of surgical and medical treatment), the procedure should be performed only in selected patients, enrolled in prospective, controlled studies.

Angioplasty, Balloon, Coronary↗