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Biomedical subjects

John G Webb

Publications and source records attributed to John G Webb.

At least 37 records · Page 2Linked to original sources
PubMed2005

Outcome of patients aged >or=75 years in the SHould we emergently revascularize Occluded Coronaries in cardiogenic shocK (SHOCK) trial: do elderly patients with acute myocardial infarction complicated by cardiogenic shock respond differently to emergent revascularization?

BACKGROUND: In the SHOCK trial, the group of patients aged >or=75 years did not appear to derive the mortality benefit from early revascularization (ERV) versus initial medical stabilization (IMS) that was seen in patients aged <75 years. We sought to determine the reason for this finding by examining the baseline characteristics and outcomes of the 2 treatment groups by age. METHODS: Patients with cardiogenic shock (CS) secondary to left ventricular (LV) failure were randomized to ERV within 6 hours or to a period of IMS. We compared the characteristics by treatment group of patients aged >or=75 years and of their younger counterparts. RESULTS: Of the 56 enrolled patients aged >or=75 years, those assigned to ERV had lower LV ejection fraction at baseline than IMS-assigned patients (27.5% +/- 12.7% vs 35.6% +/- 11.6%, P = .051). In the elderly ERV and IMS groups, 54.2% and 31.3%, respectively, were women ( P = .105) and 62.5% and 40.6%, respectively, had an anterior infarction (P = .177). The 30-day mortality rate in the ERV group was 75.0% in patients aged >or=75 years and 41.4% in those aged <75 years. In the IMS group, 30-day mortality was 53.1% for those aged >or=75 years, similar to the 56.8% for patients aged <75 years. CONCLUSIONS: Overall, the elderly randomized to ERV did not have better survival than elderly IMS patients. Despite the strong association of age and death post-CS, elderly patients assigned to IMS had a 30-day mortality rate similar to that of IMS patients aged <75 years, suggesting that this was a lower-risk group with more favorable baseline characteristics. The lack of apparent benefit from ERV in elderly patients in the SHOCK trial may thus be due to differences in important baseline characteristics, specifically LV function, and play of chance arising from the small sample size. Therefore, the SHOCK trial overall finding of a 12-month survival benefit for ERV should be viewed as applicable to all patients, including those >or=75 years of age, with acute myocardial infarction complicated by CS.

Age Factors↗
PubMed2005

N-acetylcysteine for prevention of radiographic contrast material-induced nephropathy: is the intravenous route best?

Use of oral N-acetylcysteine for preventing radiographic contrast material-induced nephropathy (RCIN) has become widespread, despite conflicting results from clinical trials and meta-analyses. The variability in study results may reflect differences in baseline risks in study patients, hydration regimens, choice of contrast agent, definition of RCIN, and the oral dosage formulation of N-acetylcysteine used. Injectable N-acetylcysteine recently has become available in the United States. Although oral N-acetylcysteine regimens are typically administered during a 48-hour period, more rapid intravenous administration could offer an important advantage for urgent procedures such as coronary angiography. However, the three published studies in which intravenous N-acetylcysteine protocols were used have produced divergent results, likely because of substantially different dosage regimens. With few intravenous studies available, clinicians may look to more broadly studied oral regimens to estimate equivalent intravenous dosages. In the oral studies, however, a wide range of formulations were used, and the bioavailability of each product was uncertain. In addition, the intravenous route circumvents first-pass metabolism, resulting in less glutathione production, perhaps compromising the antioxidant effects of N-acetylcysteine administration. Overall, little evidence exists that any studied N-acetylcysteine protocol improves clinical outcomes in terms of reducing length of hospital stay, need for dialysis, or mortality. Furthermore, N-acetylcysteine may directly affect serum creatinine level, which all clinical trials to date have used as a primary outcome measure. If oral or intravenous N-acetylcysteine is used with the intention of preventing RCIN, more established preventive measures should not be overlooked, including adequate hydration with isotonic saline, avoidance of potentially nephrotoxic drugs, and use of iso-osmolar radiographic contrast media.

Acetylcysteine↗
PubMed2004

Cardiac power is the strongest hemodynamic correlate of mortality in cardiogenic shock: a report from the SHOCK trial registry.

OBJECTIVES: We sought to analyze clinical, angiographic, and outcome correlates of hemodynamic parameters in cardiogenic shock. BACKGROUND: The significance of right heart catheterization in critically ill patients is controversial, despite the prognostic importance of the derived measurements. Cardiac power is a novel hemodynamic parameter. METHODS: A total of 541 patients with cardiogenic shock who were enrolled in the SHould we emergently revascularize Occluded Coronaries for cardiogenic shocK (SHOCK) trial registry were included. Cardiac power output (CPO) (W) was calculated as mean arterial pressure x cardiac output/451. RESULTS: On univariate analysis, CPO, cardiac power index (CPI), cardiac output, cardiac index, stroke volume, left ventricular work, left ventricular work index, stroke work, mean arterial pressure, systolic and diastolic blood pressure (all p < 0.001), coronary perfusion pressure (p = 0.002), ejection fraction (p = 0.013), and pulmonary artery systolic pressure (p = 0.047) were associated with in-hospital mortality. In separate multivariate analyses, CPO (odds ratio per 0.20 W: 0.60 [95% confidence interval, 0.44 to 0.83], p = 0.002; n = 181) and CPI (odds ratio per 0.10 W/m(2): 0.65 [95% confidence interval, 0.48 to 0.87], p = 0.004; n = 178) remained the strongest independent hemodynamic correlates of in-hospital mortality after adjusting for age and history of hypertension. There was an inverse correlation between CPI and age (correlation coefficient: -0.334, p < 0.001). Women had a lower CPI than men (0.29 +/- 0.11 vs. 0.35 +/- 0.15 W/m(2), p = 0.005). After adjusting for age, female gender remained associated with CPI (p = 0.032). CONCLUSIONS: Cardiac power is the strongest independent hemodynamic correlate of in-hospital mortality in patients with cardiogenic shock. Increasing age and female gender are independently associated with lower cardiac power.

Aged↗
PubMed2004

Procedural efficacy and complications of X-Sizer thrombectomy in de novo and stented lesions.

Angiographic thrombus is associated with poorer procedural and clinical outcomes. We report our experience with the X-Sizer thrombectomy device (EndiCOR Medical) from March 2001 to December 2002. Indications for use in 44 patients (33 male; mean age, 60) included myocardial infarction (27), unstable angina (6), periprocedural thrombosis (2), acute (< 24 hr) stent thrombosis (1), and subacute (> 24 hr) stent thrombosis (8). Three cases involved vein grafts. Deployment was successful in 42/44. Difficulty traversing the stent occurred in 5/9 cases of in-stent thrombosis. Median TIMI flow increased from 1 to 2 (P = 0.01) postthrombectomy. Median final TIMI flow was 3. Complications included dissection (1), perforation, device jam on stent (1), disruption of a covered stent (1), distal macro-embolization (4), and transient no-reflow (5). The X-Sizer thrombectomy device improves TIMI flow but does not always prevent distal embolization. Care is needed when treating in-stent thrombosis.

Cardiac Catheterization↗
PubMed2004

Percutaneous stent-mounted valve for treatment of aortic or pulmonary valve disease.

The objective of this study was to develop a prosthetic cardiac valve designed for percutaneous transcatheter implantation. Percutaneous catheter-based therapies play a limited role in the management of cardiac valve disease. Surgical implantation of prosthetic valves usually requires thoracotomy and cardiopulmonary bypass. The stent-valve is constructed of a rolled sheet of heat-treated nitinol. Although malleable when cooled, once released from a restraining sheath at body temperature the stent unrolls, becomes rigid, and assumes its predetermined cylindrical conformation. A ratcheting lock-out mechanism prevents recoil and external protrusions facilitate anchoring. Valve leaflets are constructed of bovine pericardium. The feasibility of catheter implantation, prosthetic valve function, and survival were investigated in an animal model. In vitro and pulse duplicator testing documented valve durability. Endovascular delivery of the prototype stent-valve to the aortic or pulmonary position was feasible. Accurate positioning was required to ensure exclusion of the native valve leaflets and, in the case of the aortic valve, to avoid compromise of the coronary ostia or mitral apparatus. Oversizing of the stent in relation to the valve annulus was desirable to facilitate anchoring and prevent paravalvular insufficiency. Stent-valve implantation proved feasible and compatible with survival in an animal model. Transcatheter implantation of prosthetic valves is possible. Further evolution of this technology will involve lower-profile devices with design features that facilitate vascular delivery, visualization, positioning, deployment, and valvular function.

Animals↗
PubMed2004

A randomized controlled trial of intravenous N-acetylcysteine for the prevention of contrast-induced nephropathy after cardiac catheterization: lack of effect.

BACKGROUND: Contrast-induced nephropathy (CIN) after cardiac catheterization is common in patients with preexisting renal dysfunction. Studies of oral acetylcysteine to prevent CIN have produced conflicting results. Intravenous N-acetylcysteine (NAC) has logistic advantages in this setting. The objective of this study was to evaluate, in a blinded, randomized, placebo-controlled fashion, whether intravenous NAC reduced CIN in the setting of cardiac catheterization in patients with preexisting renal insufficiency. METHODS: Patients with renal dysfunction undergoing cardiac catheterization were randomly assigned to intravenous NAC 500 mg immediately before the procedure or placebo. All patients received isotonic saline (200 mL) beforehand, followed by 1.5 mL/kg per hour for 6 hours, unless contraindicated. Exclusion criteria included acute renal failure, creatinine >400 micromol/L, concurrent dialysis, unstable clinical status, and prior NAC use. Baseline creatinine was obtained immediately before the procedure and repeated 2 to 8 days later. The primary end point was the occurrence of CIN defined as a reduction in creatinine clearance from baseline of >5 mL/min (Cockcroft-Gault formula). RESULTS: The study was terminated early because of a determination of futility by the Data Safety Monitoring Committee after enrollment of 487 patients. The median baseline creatinine clearance was 44 mL/min (interquartile range, 33, 55). Median contrast received was 120 mL (interquartile range, 80, 175). Baseline characteristics were similar in the two groups. Altogether, 98 (22.0%) subjects had the primary end point: 23.3% in the NAC group and 20.7% in the placebo arm (P =.57). CONCLUSIONS: In this large, randomized trial, enrolling a high-risk group of patients with impaired renal function, intravenous NAC was ineffective in preventing CIN.

Acetylcysteine↗
PubMed2004

Heyde's syndrome: a review.

Bleeding from gastrointestinal angiodysplasia in patients with aortic stenosis (AS), termed Heyde's syndrome, has been recognized for many years. Intestinal angiodysplasia (IA) and AS are chronic degenerative diseases that are often asymptomatic, with a higher prevalence in the population than is clinically apparent. The incidence of both conditions increases with age, and both are associated with traditional cardiovascular risk factors. Many studies suggest that there is an increased prevalence of IA in AS and vice versa, but there is wide variation between studies. Evidence is mounting that severe AS may cause Type 2 acquired von Willebrand's disease, also termed von Willebrand's syndrome. This involves loss of the large multimers, which are required to maintain hemostasis in high flow conditions, such as occur in angiodysplastic arteriovenous malformations. Heyde's syndrome appears to consist of bleeding from previously latent intestinal angiodysplasia as a result of this acquired hematological defect, which is associated with aortic stenosis. Treatment options include localization of angiodysplastic bleeding points with cauterization, but this is associated with a high recurrence rate. Aortic valve replacement has been shown to improve the hematological abnormalities, and this is paralleled by clinical improvements. Valve replacement appears to offer the best hope of long-term resolution of the bleeding, and should be considered in most cases, particularly in those in whom the AS is symptomatic. In those patients deemed unfit for surgery in whom no bleeding point can be identified, recurrent blood transfusions may offer some symptomatic relief.

Angiodysplasia↗
PubMed2003

Percutaneous coronary intervention for cardiogenic shock in the SHOCK trial.

OBJECTIVES: We examined the clinical, angiographic, and procedural characteristics determining survival after percutaneous coronary intervention (PCI) for cardiogenic shock. BACKGROUND: The SHOCK (SHould we emergently revascularize Occluded coronaries for Cardiogenic shocK?) trial prospectively enrolled patients with shock complicating acute myocardial infarction (MI). Patients were randomized to a strategy of early revascularization or initial medical stabilization. METHODS: Patients randomized to early revascularization underwent PCI or bypass surgery on the basis of predefined clinical criteria. Patients randomized to early revascularization who underwent PCI and had angiographic films available for analysis are the subject of this report (n = 82). RESULTS: The median time from MI to PCI was 11 h. The majority of patients had occluded culprit arteries (Thrombolysis In Myocardial Infarction [TIMI] grade 0 or 1 flow in 62%) and multivessel disease (81%). One-year mortality in PCI patients was 50%. Mortality was 39% if PCI was successful but 85% if unsuccessful (p < 0.001). Mortality was 38% if TIMI flow grade 3 was achieved, 55% with TIMI grade 2 flow, and 100% with TIMI grade 0 or 1 flow (p < 0.001). Mortality was 67% if severe mitral regurgitation was documented. Independent correlates of mortality were as follows: increasing age (p < 0.001), lower systolic blood pressure (p = 0.009), increasing time from randomization to PCI (p = 0.019), lower post-PCI TIMI flow (0/1 vs. 2/3) (p < 0.001), and multivessel PCI (p = 0.040). CONCLUSIONS: Restoration of coronary blood flow is a major predictor of survival in cardiogenic shock. Benefit appears to extend beyond the generally accepted 12-h post-infarction window. Surgery should be considered in shock patients with severe mitral insufficiency or multivessel disease not amenable to relatively complete percutaneous revascularization.

Aged↗
PubMed2003

Correlates of one-year survival inpatients with cardiogenic shock complicating acute myocardial infarction: angiographic findings from the SHOCK trial.

OBJECTIVES: The goal of this study was to describe the core laboratory angiographic findings of "SHould we emergently revascularize Occluded Coronaries for cardiogenic shocK" (SHOCK) trial participants and to determine the relationship of angiographic parameters to one-year survival. BACKGROUND: In the SHOCK trial, emergency revascularization improved one-year survival of patients with cardiogenic shock compared with initial medical stabilization including thrombolysis and intraaortic balloon counterpulsation. METHODS: Coronary angiography was performed by protocol in 147 of 152 (97%) patients in the emergency revascularization (ERV) group and by clinical selection in 100 of 150 (67%) patients in the initial medical stabilization (IMS) group. Of the other 50 IMS patients, 45 of 50 (90%) died rapidly and did not undergo angiography. RESULTS: Left ventricular ejection fraction was correlated with one-year survival in both treatment groups (p < 0.001). In the IMS group, the hazard ratio for death was 2.59 (95% confidence interval 1.47 to 4.58, p = 0.001) per diseased vessel (0/1 vs. 2 vs. 3). In the ERV group, the hazard ratio for death per diseased vessel was 1.11 (95% confidence interval 0.79 to 1.56, p = 0.559). Multivariate analysis of the angiography cohort (without regard for left ventriculogram measurements) identified initial Thrombolysis in Myocardial Infarction flow grade (p = 0.032), number of diseased vessels (for IMS patients only, p = 0.024), and culprit vessel (p = 0.004) as independent correlates of one-year survival, even after adjustment for key clinical factors. In the smaller cohort with left ventricular ejection fraction measured (n = 97), ejection fraction and culprit vessel remained independently correlated with survival. CONCLUSIONS: For patients in cardiogenic shock, left ventricular function and culprit vessel were independent correlates of one-year survival.

Aged↗
PubMed2003

An unusual complication of coil embolization of a large coronary-pulmonary fistula.

A 58-year-old man with hemoptysis was found to have a large fistula from his circumflex artery to the pulmonary system. Coil embolization was performed. This resulted in occlusion of the fistula, including a small branch likely supplying the sinus node. Following the procedure he developed junctional bradycardia but remained hemodynamically stable. He had a brief period of atrial fibrillation which, after 48 hours, reverted to a rhythm from an ectopic focus in the low right atrium. This case highlights an unusual complication of fistula embolization and emphasizes the need for caution when occluding vessels which may supply the sinus node.

Atrial Fibrillation↗
PubMed2002

Stenting for coronary artery spasm.

We evaluated coronary stenting in nine patients with clinically severe, angiographically documented spasm refractory to aggressive pharmacologic management. No patient subsequently developed unstable ischemia requiring hospitalization as a consequence of recurrent spasm within the stent. Mechanisms of therapeutic failure included both persistent spasm and spasm in a different artery in one patient. Restenosis occurred in three patients who subsequently underwent repeat revascularization. In the rare, carefully selected patient, stents may represent an adjunct in the management of focal coronary artery spasm, although currently medical therapy remains the standard initial approach.

Adult↗
PubMed2002

Repeated Günther Tulip inferior vena cava filter repositioning to prolong implantation time.

A patient presented with iliofemoral deep vein thrombosis, a small pulmonary embolism, and a paradoxic embolus to the axillary artery resulting from a patent foramen ovale (PFO). As prophylaxis against further paradoxic emboli while awaiting percutaneous PFO closure, a Günther Tulip inferior vena cava (IVC) filter was implanted. To prevent incorporation of the IVC filter into the caval wall, it was repositioned twice with use of a filter retrieval set from a transjugular approach. In this way, the implantation time of the filter was extended beyond the recommended period of 10 days. The filter was successfully retrieved 19 days later during percutaneous closure of the PFO.

Adult↗