Pressure-flow relations in the pulmonary artery during myocardial ischaemia: implications for right ventricular function in coronary disease

Because exercise induced pulmonary hypertension may disturb optimal coupling between the right ventricle and pulmonary artery in coronary artery disease, high fidelity pulmonary artery and right ventricular pressure and electromagnetic pulmonary artery flow velocity data were recorded at rest and during supine exercise in 10 control subjects free of detectable cardiovascular disease and in 11 patients with coronary artery disease. The pulmonary artery impedance and power spectra were calculated from Fourier analysis of pressure and flow waveforms. Total hydraulic power expended per unit of forward flow was computed as an index of right ventricular-pulmonary artery coupling. In coronary artery disease exercise produced substantial increases in pulmonary artery pressure, pulmonary artery characteristic impedance, and total power per unit flow. These changes did not occur in control subjects. Despite a significant exercise increase in right ventricular end diastolic pressure and peak right ventricular dP/dt, and independent of the presence of right coronary artery involvement, the right ventricular stroke output response during exercise was significantly blunted in the coronary artery disease patients. Pulmonary vascular resistance was unchanged by exercise in either group. Exercise induced ischaemia presents an increased pulsatile hydraulic load to the right ventricle. Increased pulmonary artery input impedance impairs the hydraulic efficiency of right ventricular-pulmonary artery coupling and may contribute to the limitation of right ventricular ejection performance in coronary artery disease.     

Changes in the practice of percutaneous coronary intervention: a comparison of enrollment waves in the National Heart, Lung, and Blood Institute (NHLBI) Dynamic Registry

The National Heart, Lung, and Blood Institute Dynamic Registry includes 15 clinical sites in wave 1, and 16 sites in wave 2 as well as a data-coordinating center. The first wave of enrollment began in July 1997 and was completed in February 1998. The second wave began in February 1999 and ended in June 1999. There were a total of 2,526 patients in wave 1 and 2,109 patients in wave 2. Comprehensive pre-, intra-, and postprocedure (in-hospital) data were analyzed for changes between recruitment waves. Patients in wave 2 were more frequently nonwhite (p < or = 0.001), hypertensive by history (p < or = 0.001), had more significant noncardiac comorbidity (p < or = 0.01), and had more frequently undergone prior percutaneous coronary intervention (p < 0.05). Patients in wave 2 underwent percutaneous coronary intervention in a setting of acute coronary syndromes more frequently than wave 1 patients (p < or = 0.001). However, most interventions in both waves were performed on 1 vessel, irrespective of the extent of disease. Attempted lesions in wave 2 were longer (p < or = 0.001), less frequently totally occluded (p < or = 0.001), and more frequently in vessels with a prior stent (p < or = 0.01). Using the American Heart Association/American College of Cardiology lesion classification scheme, attempted lesions in wave 2 were less complex than those in wave 1 (p < or = 0.001). Stent use increased significantly from wave 1 (67%) to wave 2 (79%, p < or = 0.001) as did the use of platelet glycoprotein IIb/IIIa antagonists (wave 1, 24%; wave 2, 32%: p < 0.001). Procedural outcomes (angiographic success without major in-hospital adverse events) were excellent in both waves 1 (94.6%) and 2 (95.6%) and were not significantly different. However, the frequency of significant procedural coronary dissection and in- and out-of-laboratory abrupt closure were significantly less in wave 2 (p < or = 0.001) Discharge medications were more likely to include angiotensin-converting enzyme inhibitors, beta-adrenergic blocking agents, and hypolipidemic treatment in wave 2 than in wave 1 (p < or = 0.001). These data indicate a continuing aggressive approach to patient care over the time interval analyzed. Although overall procedural outcomes are excellent, procedural safety has been further enhanced. There is also a growing awareness of the importance of secondary prevention among interventional cardiologists.     

A simplified lesion classification for predicting success and complications of coronary angioplasty. Registry Committee of the Society for Cardiac Angiography and Intervention

In 1988, the American College of Cardiology/American Heart Association (ACC/AHA) Task Force on Assessment of Diagnostic and Therapeutic Cardiovascular Procedures presented a classification of coronary lesions utilizing 26 lesion features to predict the success and complications of balloon angioplasty. Using data from the Registry of the Society for Cardiac Angiography and Interventions (SCAI) we evaluated the ability of this classification to predict success and complications. Lesion success, death in hospital, emergency cardiac bypass surgery, and major adverse events were evaluated in 41,071 patients who underwent single-vessel angioplasty from January 1993 to June 1996. Logistic models using the ACC/AHA lesion classification, vessel patency, or both, were compared. A new classification based on the interaction of the ACC/AHA classification plus lesion patency was compared with the existing ACC/AHA classification. Vessel patency, added to the ACC/AHA classification, improved prediction of lesion success (p 相似文献   

Reactions of cysteines substituted in the amphipathic N-terminal tail of a bacterial potassium channel with hydrophilic and hydrophobic maleimides

Single cysteine-substitution mutants of KcsA, a K(+) channel from Streptomyces lividans, were expressed in Escherichia coli, and inner membranes were isolated. The rate constants for the reactions of these cysteines with three maleimides of increasing hydrophobicity, 4-(N-maleimido)phenyltrimethylammonium, N-phenylmaleimide, and N-(1-pyrenyl)maleimide, were determined by back titration of the remaining cysteines with methoxypolyethylene glycol-2-pyridine disulfide (M(r) 3,000) and quantitation of the fraction of gel-shifted KcsA as a function of reaction time. The patterns of the rate constants for the reactions of all three reagents with eight consecutive cysteines in the partially lipid-immersed amphipathic N-terminal tail helix were the same, with cysteines on the hydrophilic side of the helix reacting faster than Cys on the hydrophobic side. The results are consistent with the tail helix lying with its long axis in the lipid-water interface and with the orientation of the helix fluctuating around this axis. The patterns of the rate constants for the three reagents were similar to the pattern of the probabilities that the substituted cysteines were exposed to water, based on the sum of the free energies of transfer from water to octanol of all of the residues exposed to lipid in each orientation of the helix.     

Variability in fluoroscopic X-ray exposure in contemporary cardiac catheterization laboratories.

OBJECTIVES: This study sought to assess fluoroscopic exposure rates in contemporary cardiac catheterization laboratories (CCL). BACKGROUND: Increasing attention is being focused on X-ray exposure during diagnostic and therapeutic cardiovascular procedures. METHODS: We measured fluoroscopic exposure rates (R/min) in 41 systems using a standardized methodology (National Electrical Manufacturers Association XR21 phantom). Measurements were obtained at 2 different phantom thicknesses to simulate varying patient body habitus. RESULTS: Fluoroscopic exposure rates under medium (median 3.0 R/min, interquartile range 1.4 R/min) and large (median 12.5 R/min, interquartile range 4.8 R/min) habitus conditions showed substantial variation. Fluoroscopic exposure was associated with simulated patient habitus, X-ray system type, vendor, and geographic region. Under medium habitus conditions, only 25% of systems operated within a zone of lower than average exposure rates and satisfactory image quality; this frequency diminished to 7% under large habitus conditions (p < 0.001). CONCLUSIONS: There is substantial variation (4- to 6-fold) in fluoroscopic exposure rates. This variation was not consistently associated with improved image quality. In the absence of a predictable benefit of higher (or lower) than average exposure rates, CCL quality improvement programs must minimize such potentially harmful variability in X-ray exposure.     

Atorvastatin does not induce glomerular or tubular dysfunction even at high doses

The current analyses evaluated the effect of atorvastatin on biomarkers of renal function. Serum creatinine level and markers of tubular and glomerular function, including cystatin C, urine N-acetyl-beta-D-glucosaminidase, urine and serum beta2-microglobulin, and urine albumin, were assessed in osteopenic postmenopausal women with mild dyslipidemia who received atorvastatin 20 mg, atorvastatin 80 mg, or placebo for 1 year. During the study, changes in serum creatinine levels were the same in all 3 treatment groups. Cystatin C levels remained unchanged in all groups at all time points. For the additional markers of renal function, median values at baseline and weeks 26 and 52 in both of the atorvastatin and the placebo groups were similar. Neither moderate- nor high-dose atorvastatin treatment for 1 year altered markers of glomerular and renal tubular function compared with placebo. These data indicate that in this patient population, atorvastatin, even at a high dose, does not interfere with renal tubular reabsorption of protein, induce renal tubular dysfunction, or alter glomerular filtration rate in humans.     

Left ventricular mechanical load and contractile function in patients with chronic mitral regurgitation

BACKGROUND AND AIM of the study: Left ventricular adaptation to chronic volume overload results in dramatic changes in ventricular geometry and hemodynamics. These changes are reflected in alterations in mechanical load and, eventually, contractile function. METHODS: The study included 17 patients undergoing clinically driven invasive evaluation for mitral regurgitation (MR). Simultaneous catheter-tip manometry and M-mode echocardiography allowed for derivation of meridional and circumferential wall stress at end-diastole, end-systole, peak systole, and the average over the systolic ejection period. Assessment of contractile function was performed by analysis of: the overall group relationship between baseline end-systolic stress (ESS) and end-systolic dimension (ESD); subject-specific analysis of the relationship between ESS and ESD derived from pharmacologic load alteration; and subject- specific analysis of the relationship between left ventricular minor axis shortening and ESS. The acquired data were compared to data from 10 control subjects who were undergoing invasive evaluation and were free from cardiovascular disease. RESULTS: Compared to controls, patients with chronic MR (mean regurgitant fraction 57%) were characterized by significantly increased angiographic end-diastolic and end-systolic volumes, lower cardiac indices, and similar left ventricular ejection fractions. Patients with chronic MR were also characterized by increased preload (end-diastolic stress) and afterload (mean systolic stress). ESS was not consistently increased in these patients, despite the increased chamber size. The severity of clinical symptoms was associated with the magnitude of alteration in afterload (mean systolic stress). Using different methodologies, a substantial prevalence of depressed contractile function was identified in those patients with preserved ejection fraction. CONCLUSION: When compared to an age- and gender-matched controls, symptomatic patients with MR have similar left ventricular ejection performance in the setting of increased pre-load and after-load. Symptom severity was associated with increased afterload. The prevalence of contractile dysfunction in this setting was substantial.