PubMed Health⌕ Search

Biomedical subjects

T R Bowers

Publications and source records attributed to T R Bowers.

12 recordsLinked to original sources
PubMed1998

Effect of reperfusion on biventricular function and survival after right ventricular infarction.

BACKGROUND: Although the salutary effects of reperfusion in patients with left ventricular infarction are well documented, the benefits in patients with acute right ventricular infarction are less clear. METHODS: To determine whether primary angioplasty improves right ventricular function and the clinical outcome in patients with right ventricular infarction, we performed echocardiographic studies before and after angioplasty in 53 patients with acute right ventricular infarction. RESULTS: Complete reperfusion, defined as normal flow in the right main coronary artery and its major right ventricular branches, was achieved in 41 patients (77 percent), leading to prompt and striking recovery of right ventricular function (mean [+/-SE] score for free-wall motion, 3.0+/-0.1 at base line and 1.4+/-0.1 at three days; P<0.001). Twelve patients (23 percent) had unsuccessful reperfusion, defined as the failure to restore right ventricular branch flow, with or without patency of the right main coronary artery. Unsuccessful reperfusion was associated with lack of recovery of right ventricular function (score for free-wall motion, 3.2+/-0.2 at base line and 3.0+/-0.9 at three days; P= 0.55), as well as persistent hypotension and low cardiac output (in 83 percent of the patients, vs. 12 percent of those with successful reperfusion; P=0.002) and a high mortality rate (58 percent, vs. 2 percent for those with successful reperfusion; P=0.001). CONCLUSIONS: In patients with right ventricular infarction, complete reperfusion of the right coronary artery by angioplasty results in the dramatic recovery of right ventricular performance and an excellent clinical outcome. In contrast, unsuccessful reperfusion is associated with impaired recovery of right ventricular function, persistent hemodynamic compromise, and a high mortality rate.

Angioplasty, Balloon, Coronary↗
PubMed1997

Incidence and angiographic predictors of side branch occlusion following high-pressure intracoronary stenting.

We evaluated the incidence, angiographic predictors, and clinical outcome of side branch occlusion (SBO) following high-pressure intracoronary stenting in 175 patients. All stent implants during a 7-month period were reviewed for the incidence of major (>1 mm) SBO. Side branches were further characterized based on side branch and index lesion morphology. Clinical events (death, myocardial infarction, and target vessel revascularization rates) were determined at 9 months. A total of 175 patients (182 lesions) had 224 major side branches covered by intracoronary stents. Of these, 43 (19%) occluded. Most SBOs (29 of 43 [67%]) occurred after poststent dilation using high-pressure inflations (15.3 +/- 3.3 atmospheres). No clinical characteristics correlated with SBO. By multivariate analysis, those side branches with >50% ostial narrowing that arose from within or just beyond the diseased portion of the parent vessel (threatened side branch morphologies) were a powerful angiographic predictor of SBO (odds ratio 40, 95% confidence interval, 14 to 130, p <0.0001). At 9-month follow-up there was no difference in combined clinical events between those patients with and without SBO. These data demonstrate that side branches with ostial stenoses in continuity with diseased parent lesions were at risk of occlusion following stenting. SBO, however, was not associated with adverse clinical outcome. These findings lend support to plaque shift ("snow plow effect") as the mechanism behind SBO following stent placement.

Aged↗
PubMed1997

Effect of Rotablator atherectomy and adjunctive balloon angioplasty on coronary blood flow.

BACKGROUND: The purpose of this study was to assess serial changes in coronary blood flow velocity before and after Rotablator atherectomy and after adjunctive percutaneous transluminal coronary angioplasty (PTCA). Since Rotablator atherectomy results in luminal enlargement by plaque pulverization and distal embolization, improvement in coronary blood flow could be attenuated despite luminal enlargement. METHODS AND RESULTS: Intracoronary Doppler blood flow velocity measurements were obtained with a Doppler Flowire. Basal average peak velocity (bAPV), hyperemic APV (hAPV), diastolic/systolic velocity ratio (DSVR), and coronary flow reserve (CFR) were assessed before intervention, after Rotablator, and after adjunctive PTCA. Complete clinical, angiographic, and Doppler data were obtained in 22 patients. There was a small but significant difference (P = .02) in resting heart rate and mean arterial pressure before and after Rotablator and after adjunctive PTCA. Minimum lumen diameter increased from 0.8 +/- 0.1 to 1.5 +/- 0.2 to 2.0 +/- 0.1 mm (P < .001), corresponding to decreases in diameter stenosis from 72 +/- 3% to 41 +/- 4% to 36 +/- 3% (P < .001). Although bAPV, hAPV, and DSVR increased significantly (P < .001), CFR remained abnormally low in 19 of 22 patients (despite an increase from baseline to post-PTCA). hAPV > 30 cm/s was the best Doppler correlate of angiographic success. CONCLUSIONS: Rotablator atherectomy and adjunctive PTCA significantly improve distal coronary blood flow velocity and DSVR but not CFR. Failure to normalize CFR could be secondary to parallel increases in bAPV and hAPV, "acquired" microvascular disease due to distal microembolization or spasm, and/or angiographically inapparent dissection or residual stenosis. Adjunctive PTCA contributes significantly to the overall physiological benefit of a combined procedure.

Aged↗
PubMed1997

PET perfusion and vasodilator function after angioplasty for acute myocardial infarction.

UNLABELLED: The aims of this study were to validate invasive coronary Doppler flows against noninvasive PET assessments of myocardial perfusion and to examine the timing and degree of regional coronary vasodilator reserve recovery in patients who are successfully reperfused with primary angioplasty (PTCA) for acute myocardial infarction. METHODS: PTCA was performed in 21 consecutive patients with acute myocardial infarction; the final diameter stenosis was 25% +/- 7%. After restoration of TIMI Grade 3 flow, all patients underwent quantitative coronary angiography and distal Doppler coronary blood flow studies (basal and after adenosine-induced hyperemia) in the infarct and noninfarct vessels. Regional myocardial perfusion and vasodilator function were quantitated after intravenous adenosine infusion PET in all patients at 26 +/- 9 hr after acute PTCA. These were repeated in 17 patients 9 +/- 3 days later. RESULTS: Post-PTCA resting coronary flow was 35 +/- 15 ml/min in the infarct-related vessels and 50 +/- 24 ml/min during peak hyperemia (p < 0.05). Coronary flow reserve (CFR) was 1.48 +/- 0.34 and 2.08 +/- 0.62 in the infarct and noninfarct vessels, respectively (p < 0.001). Early (< 36 hr) PET myocardial perfusion reserves (MPR) in the infarct and noninfarct regions were 1.59 +/- 0.33 and 2.03 +/- 0.62 (p < 0.01). Doppler CFR and PET MPR were correlated in the infarct (r = 0.61, p < 0.01) and noninfarct (r = 0.77, p < 0.0001) regions. Follow-up PET studies demonstrated improved MPR in both infarct and noninfarct regions (1.93 +/- 0.52 versus 2.54 +/- 0.97, p < 0.01). The improvement in coronary vasodilator function from the time of acute PTCA to follow-up PET in the infarct region was significant (p = 0.005). CONCLUSION: After successful mechanical revascularization by PTCA after acute myocardial infarction, intracoronary Doppler blood flows and noninvasive PET regional myocardial perfusion are correlated within the wide range of reperfusion blood flows observed in patients with contrast angiographic TIMI Grade 3 flow. Serial PET studies demonstrated a trend towards continued improvement in the vasodilator response in infarct-related myocardial regions after the restoration of blood flow by PTCA. PET offers the potential for accurate noninvasive serial assessment of reperfusion blood flow after primary angioplasty for acute myocardial infarction.

Angioplasty, Balloon, Coronary↗
PubMed1996

Effect of reperfusion modality on outcome in nonsmokers and smokers with acute myocardial infarction (a Primary Angioplasty in Myocardial Infarction [PAMI] substudy). PAMI Investigators.

We analyzed the 395 patients randomized into the Primary Angioplasty in Myocardial Infarction (PAMI) trial to receive tissue plasminogen activator (tPA) or to undergo primary percutaneous transluminal coronary angioplasty (PTCA) for acute myocardial infarction (AMI). Of these, 168 were current smokers and 128 had never smoked. Univariate analyses of baseline characteristics and outcome, including death, recurrent AMI, and recurrent ischemia, were done by chi-square analysis. Multivariate stratified analysis was then performed controlling for age and gender, which were found to be confounders of outcome. The combined in-hospital outcomes of death, recurrent AMI, and recurrent ischemia were similar for smokers and nonsmokers (p = 0.12). When stratified according to treatment modality, non-smokers treated with PTCA had a lower frequency of death and nonfatal recurrent AMI (7% vs 18%; p = 0.05), in-hospital ischemia (11% vs 33%; p = 0.004), or the combined event (13% vs 40%; p = 0.001). At 6 months, nonsmokers treated with PTCA continued to have a lower incidence of death or nonfatal recurrent AMI (11% vs 24%; p = 0.07) compared with tPA. Conversely, in smokers, the treatment strategy did not significantly affect hospital outcomes: recurrent ischemia (12% vs 23%; p = 0.07), death and recurrent AMI (6% vs 8%; p = 0.55), or the combined event (15% vs 25%; p = 0.12). The statistical significance of these associations was maintained when multivariate analysis controlling for age and gender was used. Thus, nonsmokers presenting with AMI had a significantly better outcome when treated with primary angioplasty; these differences were not seen in smokers.

Aged↗
PubMed1996

Treatment of no-reflow in degenerated saphenous vein graft interventions: comparison of intracoronary verapamil and nitroglycerin.

No-flow has been reported after 10-15% of percutaneous interventions on degenerated saphenous vein grafts. In this prospective study of 36 degenerated saphenous vein graft lesions (32 patients), no-flow (TIMI flow < 3 in the absence of a significant lesion or dissection) occurred in 15/36 (42%) lesions. A total of 32 episodes of no-flow occurred after angioscopy (n = 14), extraction atherectomy (n = 10), balloon angioplasty (n = 2) or stent implantation (n = 6). Intragraft nitroglycerin (100-300 micrograms) alone resulted in no improvement in TIMI flow in the setting of no-reflow (TIMI flow 1.2 +/- 0.6 to 1.4 +/- 0.8, P = NS). Intragraft verapamil (100-500 micrograms) resulted in improvement in flow in all 32 episodes (TIMI flow 1.4 +/- 0.8 before, to 2.8 +/- 0.5 after verapamil, P < 0.001). Although verapamil increased TIMI flow after all episodes of no-reflow, two (6.3%) had persistent no-reflow (TIMI 1) despite verapamil, associated with non-Q wave myocardial infarction. In conclusion, treatment of no-reflow with verapamil during degenerated vein graft interventions was associated with reestablishment of TIMI 3 flow in 88% of cases. In contrast, intragraft nitroglycerin alone was ineffective for reversing no-reflow.

Aged↗
PubMed1994

Pectus excavatum: abnormal exercise scintigraphy with normal coronary arteries.

Pectus excavatum is the most common congenital abnormality of the chest wall, and is frequently associated with chest pain. The invasive, as well as the ECG and echocardiographic assessment of possible coronary artery disease (CAD) in adults with moderate to severe forms of this deformity, is often complicated by the associated displacement of the heart in the chest cavity in these patients. We present findings in a 67-yr-old male that demonstrate that the predictive accuracy of positive stress radionuclide ventriculogram (RVG) and SPECT scintigraphic studies may be significantly reduced in patients with moderate to severe forms of this abnormality. Our findings also suggest, however, that either lateral or even a shallow left posterior oblique detector positioning during RVG, a significantly revised SPECT acquisition orbit, or planar imaging may provide a more accurate means to assess possible CAD in these patients. Like-wise, physician input would appear to be invaluable in determining the optimal mode of imaging and the acquisition protocol for patients with pectus excavatum.

Adult↗
PubMed1979

Preliminary crystallographic data on monomeric and dimeric hemoglobins from the sea cucumber, Molpadia arenicola.

Large single crystals of two distinct globin chains from coelomic cells of the sea cucumber Molpadia arenicola have been prepared and examined by x-ray crystallography. These hemoglobins exhibit a variety of ligand-dependent association states with the met-hemoglobins existing as monomers and liganded hemoglobins as dimers at physiological concentrations. Monomeric methemoglobin C chain crystallizes in space group P21, with a = 46.0 A, b = 45.3 A, c = 40.9 A, beta = 104.5 degrees, and one monomer per asymmetric unit. These crystals exhibit unusual spectroscopic behavior when examined with a polarizer, turning colorless in certain orientations. This implies that all the heme rings are nearly parallel within the crystals. Dimeric cyanmethemoglobin D chain crystallizes in space group P41212 (P43212), with a = b = 77.0 A, c = 61.5 A, and one-half a dimer per asymmetric unit. These homodimers thus possess a molecular 2-fold which is aligned with the crystallographic dyad.

Animals↗