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Biomedical subjects

Andrew D Michaels

Publications and source records attributed to Andrew D Michaels.

33 records · Page 2Linked to original sources
PubMed2004

Two-year outcomes after enhanced external counterpulsation for stable angina pectoris (from the International EECP Patient Registry [IEPR]).

We assessed the long-term outcomes of enhanced external counterpulsation in relieving angina and improving the quality of life in a large cohort of patients with chronic angina pectoris. Seventy-three percent had a reduction by > or =1 angina class at the end of treatment, and 50% reported an improvement in the quality-of-life assessment after enhanced external counterpulsation; these results were sustained at 2-year follow-up.

Adult↗
PubMed2003

Effects of intravenous nesiritide on human coronary vasomotor regulation and myocardial oxygen uptake.

BACKGROUND: Nesiritide, recombinant human B-type natriuretic peptide, has been shown to be efficacious in the treatment of decompensated heart failure. The effects of intravenous nesiritide on the human coronary vasculature have not been studied. METHODS AND RESULTS: Ten patients underwent right and left heart catheterization. Baseline coronary blood flow was determined using quantitative coronary angiography (QCA) and an intracoronary Doppler-tipped guidewire. Myocardial oxygen uptake was measured using a coronary sinus catheter. Patients then received an intravenous infusion of nesiritide (2 microg/kg bolus followed by 0.01 microg/kg per min infusion) for 30 minutes. Right atrial pressure decreased 52% (P=0.012), pulmonary artery mean pressure decreased 19% (P=0.03), pulmonary capillary wedge pressure decreased 46% (P=0.002), and mean arterial pressure decreased 11% (P=0.007). QCA demonstrated a 15% increase in coronary artery diameter from a baseline of 2.6+/-0.8 to 3.0+/-0.8 mm at 30 minutes (P=0.007). The coronary velocity measure of average peak velocity increased 14% from 20.8+/-6.4 at baseline to 23.8+/-7.2 cm/s at 5 minutes (P=0.015) and then returned to baseline for the remainder of the infusion. Coronary blood flow increased 35% (P=0.007), whereas coronary resistance decreased 23% at 15 and 30 minutes (P=0.036). Myocardial oxygen uptake decreased 8% during the nesiritide infusion (P=0.043). CONCLUSIONS: Nesiritide exerts coronary vasodilator effects on both the coronary conductance and resistance arteries. Despite a decrease in coronary perfusion pressure, coronary artery blood flow is increased, coronary resistance is decreased, and myocardial oxygen uptake is decreased.

Adult↗
PubMed2002

Left ventricular systolic unloading and augmentation of intracoronary pressure and Doppler flow during enhanced external counterpulsation.

BACKGROUND: Enhanced external counterpulsation (EECP) is a noninvasive, pneumatic technique that provides beneficial effects for patients with chronic, symptomatic angina pectoris. However, the physiological effects of EECP have not been studied directly. We examined intracoronary and left ventricular hemodynamics in the cardiac catheterization laboratory during EECP. METHODS AND RESULTS: Ten patients referred for diagnostic evaluation underwent left heart catheterization and coronary angiography from the radial artery. At baseline and then during EECP, central aortic pressure, intracoronary pressure, and intracoronary Doppler flow velocity were measured using a coronary catheter, a sensor-tipped high-fidelity pressure guidewire, and a Doppler flow guidewire, respectively. Similar to changes in aortic pressure, EECP resulted in a dramatic increase in diastolic (71+/-10 mm Hg at baseline to 137+/-21 mm Hg during EECP; +93%; P<0.0001) and mean intracoronary pressures (88+/-9 to 102+/-16 mm Hg; +16%; P=0.006) with a decrease in systolic pressure (116+/-20 to 99+/-26 mm Hg; -15%; P=0.002). The intracoronary Doppler measure of average peak velocity increased from 11+/-5 cm/s at baseline to 23+/-5 cm/s during EECP (+109%; P=0.001). The TIMI frame count, a quantitative angiographic measure of coronary flow, showed a 28% increase in coronary flow during EECP compared with baseline (P=0.001). CONCLUSIONS: EECP unequivocally and significantly increases diastolic and mean pressures and reduces systolic pressure in the central aorta and the coronary artery. Coronary artery flow, determined by both Doppler and angiographic techniques, is increased during EECP. The combined effects of systolic unloading and increased coronary perfusion pressure provide evidence that EECP may serve as a potential mechanical assist device.

Adult↗
PubMed2002

Correlates of coronary blood flow before and after percutaneous coronary intervention and their relationship to angiographic and clinical outcomes in the RESTORE trial. Randomized Efficacy Study of Tirofiban for Outcomes and REstenosis.

BACKGROUND AND OBJECTIVES: Slower blood flow in the setting of acute myocardial infarction (MI) has been related to adverse outcomes, but the relationship of coronary blood flow after percutaneous transluminal coronary angioplasty (PTCA) in the setting of acute coronary syndromes to adverse outcomes and restenosis has not been well described. We sought to evaluate the correlates of pre- and post-PTCA coronary blood flow to shed light on potential modifiable determinants. METHODS: The RESTORE trial (Randomized Efficacy Study of Tirofiban for Outcomes and REstenosis) was a randomized, double-blind, placebo-controlled trial of tirofiban in patients undergoing balloon angioplasty or directional atherectomy within 72 hours of occurrence of either unstable angina pectoris or acute MI. Coronary blood flow was assessed with the corrected TIMI frame count (CTFC), and clinical outcomes were assessed at 30 days. RESULTS: In addition to tighter and longer minimum lumen diameters (MLDs), the multivariate correlates of slower flow before PTCA also included the presence of thrombus, collaterals, left coronary artery lesion location, acute MI, and >8F catheter size. As well as the above variables, type C and D dissection grades were related to slower post-PTCA CTFC. Death, or the composite of death/MI/coronary artery bypass graft at 30 days, was more frequent among patients with slower post-PTCA CTFCs and those with post-PTCA thrombus. In a multivariate model correcting for reference segment diameter and MLD, the post-PTCA CTFC was an independent predictor of late lumen loss and the follow-up MLD at 6 months. As a single index that integrates functional and anatomical aspects of the post-PTCA results, the ratio of CTFC/MLD was associated with death/MI by 30 days. CONCLUSIONS: In addition to MLD, variables such as the presence of thrombus, left coronary artery lesion location, and dissection grade also are associated with slower coronary blood flow after PTCA. In turn, post-PTCA CTFCs were an independent predictor of late lumen loss and follow-up MLDs. Furthermore, patients who die or who sustain other adverse cardiac events have slower coronary blood flow and greater thrombus burden after PTCA.

Angina, Unstable↗
PubMed2002

Pretreatment with intragraft verapamil prior to percutaneous coronary intervention of saphenous vein graft lesions: results of the randomized, controlled vasodilator prevention on no-reflow (VAPOR) trial.

BACKGROUND: Intragraft verapamil is effective in treating no-reflow during saphenous vein graft (SVG) percutaneous coronary intervention (PCI). In this study, we assessed the use of intragraft verapamil given pre-PCI to prevent no-reflow. METHODS: Patients undergoing SVG PCI were randomized to receive intragraft 200 g verapamil or no verapamil immediately prior to PCI. Pre- and post-PCI, vessel flow was assessed using TIMI flow grade and TIMI frame count by blinded angiographic readers. Tissue level perfusion in the graft territory was assessed using the TIMI myocardial perfusion grade (TMPG). CK-MB or troponin I levels were measured 6 12 hours post-PCI. RESULTS: Ten patients were randomized to the verapamil group and 12 were assigned to the placebo group. No-reflow occurred in 33.3% of the placebo group, compared to none of the verapamil patients (p = 0.10). The use of intragraft verapamil prior to SVG PCI increased flow rate in the vessel as assessed by TIMI frame count (53.3 22.4% faster in the verapamil group versus 11.5 38.9% in the placebo group; p = 0.016). There was a trend toward improved myocardial perfusion as assessed by TMPG. There was no difference in the incidence of cardiac biomarker release following PCI. CONCLUSIONS: Intragraft administration of verapamil prior to saphenous vein graft PCI reduces no-reflow and is associated with a trend toward improved myocardial perfusion.

Aged↗
PubMed2000

Importance of the TIMI frame count: implications for future trials.

Although the TIMI (Thrombolysis In Myocardial Infarction) flow grade classification scheme is widely used to assess angiographic outcomes, it is limited by poor reproducibility and its categoric nature. The corrected TIMI frame count (CTFC) is a simple, more objective continuous variable index of coronary blood flow that can be broadly and inexpensively applied. This measure of the time for dye to traverse a coronary artery is both accurate (highly correlated with Doppler velocity measurements) and precise (reproducible). The method has been prospectively validated as providing independent risk stratification above and beyond the conventional TIMI flow grades. It has been shown to be a predictor of restenosis, and has been of value in elucidating the underlying pathophysiology of acute myocardial infarction. In view of the above and its ease of use, we anticipate that CTFC will become a widely used method to evaluate coronary blood flow.

Journal Article↗
PubMedDate not supplied

Hemodynamic correlates of the third heart sound and systolic time intervals.

Bedside diagnostic tools remain important in the care of patients with heart failure. Over the past two centuries, cardiac auscultation and phonocardiography have been essential in understanding cardiac pathophysiology and caring for patients with heart disease. Diastolic heart sounds (S3 and S4) and systolic time intervals have been particularly useful in this regard. Unfortunately, auscultation skills have declined considerably, and systolic time intervals have traditionally required carotid pulse tracings. Newer technology allows the automated detection of heart sounds and measurement of systolic time intervals in a simple, inexpensive, noninvasive system. Using the newer system, the authors present data on the hemodynamic correlates of the S3 and abnormal systolic time intervals. These data serve as the foundation for using the system to better understand the test characteristics and pathophysiology of the S3 and systolic time intervals, and help to define their use in improving the bedside diagnosis and management of patients with heart failure.

Female↗
PubMedDate not supplied

Enhanced external counterpulsation in the management of angina in the elderly.

This study was undertaken to determine whether enhanced external counterpulsation is a safe and effective treatment for angina in octogenarians. In this prospective observational study, demographic and clinical outcome data on patients consecutively enrolled in the International EECP Patient Registry was examined. Of the 3037 patients analyzed, 249 (8%) were >/=80 years old. Octogenarians were more likely to be female and have a history of congestive heart failure (41% vs. 29%; p<0.001). They were less likely to have had previous revascularization. Fewer patients in the octogenarian group (76% vs. 84%; p<0.01) completed a course of treatment. Of those octogenarian patients who completed treatment, 76% reported a reduction in angina and quality of life improved significantly. Adverse events related to treatment were low. At 6-month follow-up, 81% reported maintenance of angina improvement. Thus, enhanced external counterpulsation is a low-risk intervention that offers octogenarians the ability to return to more normal activity and a better quality of life.

Adrenergic beta-Antagonists↗
PubMedDate not supplied

Is there any indication for aortic valvuloplasty in the elderly?

Elderly patients with severe symptomatic calcific aortic stenosis do poorly with medical management. The optimal treatment for this group of patients is surgical valve replacement. Balloon valvuloplasty may be useful as a bridge to aortic valve replacement in hemodynamically unstable patients, in patients undergoing emergent noncardiac surgery, and in patients with severe comorbidities who are too ill to undergo cardiac surgery. Balloon valvuloplasty often results in symptomatic improvement; however, the postvalvuloplasty valve area is usually <1.0 cm2, the major periprocedural complication rate is roughly 5%, and the 6-month restenosis rate is quite high. There is no evidence that balloon valvuloplasty alters the natural history of aortic stenosis, although no randomized study has been performed.

Aged↗
PubMedDate not supplied

Obese patients have lower B-type and atrial natriuretic peptide levels compared with nonobese.

Obesity is a risk factor for the development of heart failure, but the causal mechanism remains unclear. Impaired production or enhanced clearance of natriuretic peptides, which regulate sodium balance and sympathetic activation, may play an important role. The authors investigated the relationship of plasma B-type natriuretic peptide and atrial natriuretic peptide levels to body mass index in 100 patients referred for left heart catheterization. Hemodynamic and echocardiographic data were obtained for all study participants. Atrial natriuretic peptide and B-type natriuretic peptide levels were compared in obese (body mass index > or = 30 kg/m2) and nonobese (body mass index < 30 kg/m2) subjects. Multivariate regression analyses were performed, adjusting for clinical and hemodynamic covariates. Obese patients had significantly lower B-type natriuretic peptide (p = 0.03) and atrial natriuretic peptide (p = 0.04) levels compared with nonobese. Multivariate analysis revealed lower B-type natriuretic peptide (p = 0.095) and atrial natriuretic peptide (p = 0.007) levels in obese patients while controlling for age, sex, left ventricular end-diastolic pressure, and left ventricular ejection fraction. Low levels of circulating natriuretic peptides are thus associated with obesity and may contribute to the development of heart failure.

Atrial Natriuretic Factor↗