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Rick A Nishimura

Publications and source records attributed to Rick A Nishimura.

44 records · Page 3Linked to original sources
PubMed2002

Prevalence and age-dependence of malignant mutations in the beta-myosin heavy chain and troponin T genes in hypertrophic cardiomyopathy: a comprehensive outpatient perspective.

OBJECTIVES: The goal of this study was to determine the prevalence of "malignant" mutations in hypertrophic cardiomyopathy (HCM). BACKGROUND: Previous genotype-phenotype studies have implicated four mutations (R403Q, R453C, G716R and R719W) as highly malignant defects in the beta-myosin heavy chain (MYH7). In the cardiac troponin T gene (TNNT2), a specific mutation (R92W) has been associated with high risk of sudden death. Routine clinical screening for these malignant mutations has been suggested to identify high-risk individuals. METHODS: We screened 293 unrelated individuals with HCM seen at the Mayo Clinic in Rochester, Minnesota, between April 1997 and October 2000. Deoxyribonucleic acid (DNA) was obtained after informed consent; amplification of MYH7 exons 13 (R403Q), 14 (R453C) and 19 (G716R and R719W), and TNNT2 exon 9 (R92W) was performed by polymerase chain reaction. The mutations were detected using denaturing high-performance liquid chromatography and automated DNA sequencing. RESULTS: The mean age at diagnosis was 42 years with 53 patients diagnosed before age 25. The mean maximal left ventricular wall thickness was 21 mm. Nearly one-third of cases were familial and one-fourth had a family history of sudden cardiac death. Only 3 of the 293 patients possessed one of the five "malignant" mutations, and all 3 patients were <25 years of age at presentation (p < 0.006). CONCLUSIONS: This finding underscores the profound genetic heterogeneity in HCM. Only 1% of unrelated individuals seen at a tertiary referral center for HCM possessed one of the five "malignant" mutations that were examined. Routine clinical testing for these specific mutations is of low yield.

Adolescent↗
PubMed2002

Strain rate imaging for assessment of regional myocardial function: results from a clinical model of septal ablation.

BACKGROUND: Regional myocardial function assessment is essential in the management of coronary artery disease (CAD). Tissue Doppler imaging (TDI) by depicting local myocardial motion can potentially quantify regional myocardial function. Strain rate imaging (SRI) that depicts regional deformation is less susceptible to cardiac translation and tethering and may be superior to TDI for regional function analysis. We examined regional myocardial function using TDI and SRI in a unique clinical model of a small, discrete myocardial infarction. METHODS AND RESULTS: Ten patients with severely symptomatic septal hypertrophy underwent basal septal ablation via intracoronary alcohol injection and had TDI and SRI pre- and postablation. Invasive hemodynamics showed no appreciable change in global function. Peak systolic strain rate was significantly lower postablation versus preablation (-0.5 versus -1.2 s(-1), P<0.001) and when comparing infarct and noninfarct areas (-0.5 versus -1.5 s(-1), P<0.001). In contrast, peak systolic tissue velocities were similar pre- and postablation (3.9 versus 2.9 cm/s, P=0.16) and between infarct and noninfarct areas (2.9 versus 2.2 cm/s, P=0.13). SRI analysis demonstrated reduced systolic function in the peri-infarct zone and preserved systolic function in the remote nonischemic zone. CONCLUSION: In the clinical setting of a small, discrete infarct unaccompanied by changes in global function, SRI accurately depicted changes in regional function. These data suggest that SRI may be the optimal method for objective, quantitative assessment of regional myocardial dysfunction.

Cardiac Catheterization↗
PubMed2002

Pulmonary venous pressure: relationship to pulmonary artery, pulmonary wedge, and left atrial pressure in normal, lightly sedated dogs.

Because pulmonary venous pressure has never been measured, it is unclear whether pulmonary wedge pressure measures left atrial pressure, as commonly assumed, or pressure more upstream in the pulmonary venous or capillary beds. Fluid-filled mean pulmonary artery and pulmonary wedge pressure were compared with pulmonary venous and left atrial pressure obtained with high-fidelity micromanometer catheters in eight lightly sedated dogs over a physiologic range of filling pressures. In all conditions, mean pulmonary wedge pressure was virtually identical (r = 0.99) to mean left atrial pressure (slope = 0.99; intercept = -0.46 mm Hg). At the same time, mean pulmonary venous pressure (17.1 +/- 6.5 mm Hg) was intermediate between mean pulmonary artery pressure (20.2 +/- 6.2 mm Hg) and mean pulmonary wedge pressure (13.3 +/- 6.2 mm Hg; P < 0.0001) or mean left atrial pressure (13.4 +/- 6.3 mm Hg; P < 0.0001). These relationships were maintained over normal and increased pressure ranges. As measured by conventional flow-directed pulmonary catheters, mean pulmonary wedge pressure accurately reflects left atrial pressure in lightly sedated, spontaneously breathing normal dogs.

Animals↗
PubMed2002

Difference in mechanical atrioventricular delay between atrial sensing and atrial pacing modes in patients with hypertrophic and dilated cardiomyopathy: an electrical hemodynamic catheterization study.

UNLABELLED: For optimal pacemaker programming in patients with cardiomyopathy, it is important to understand the relationship between the programmed right atrial and ventricular delay and the mechanical contraction delay of the left atrium and left ventricle. METHODS: We analyzed data from 34 patients with dilated cardiomyopathy (14) or hypertrophic obstructive cardiomyopathy (20) who had dual-chamber P-synchronous pacing (VDD) and atrioventricular sequential pacing (DVI) during hemodynamic catheterization. Using multiple atrioventricular intervals during VDD and DVI pacing, the relationship of the programmed right atrial-right ventricular interval to the mechanical left atrial-left ventricular delay (assessed by high-fidelity pressures) was determined. RESULTS: We found that the optimal mechanical left atrial-left ventricular delay was 120 ms, which required a programmed right atrial-right ventricular interval of 160 ms during DVI pacing. Also, the mean difference in right atrial-right ventricular pacing interval between VDD and DVI modes was 54 +/- 28 ms (range, 10-120 ms) in the hypertrophic obstructive cardiomyopathy group and 64 +/- 38 ms (range, 20-150 ms) in the dilated cardiomyopathy group. CONCLUSIONS: We concluded that the optimal right atrial-right ventricular interval during DVI pacing was 160 ms and that, to achieve the same mechanical left atrial-left ventricular delay, the programmed right atrial-right ventricular interval during VDD pacing was approximately 50 ms to 60 ms shorter than during DVI pacing. However, the difference of electrical atrioventricular pacing interval in VDD and DVI may vary widely from patient to patient.

Aged↗
PubMed2002

Detection of calcium deposits on heart valve leaflets by vibro-acoustography: an in vitro study.

The presence of calcium deposits on heart valve leaflets constitutes a clinically significant diagnostic indication. A novel method for imaging and detecting calcium deposits on tissue heart valves is presented. The method, called vibro-acoustography, uses the radiation force of ultrasound to vibrate the tissue at low (kHz) frequency and records the resulting acoustic response to produce images that are related to the hardness of the tissue. The method is tested on excised human heart valve tissues. Resulting images clearly show calcium deposits with high contrast and are in agreement with the corresponding radiographs of the specimens.

Algorithms↗