Five-year follow-up of patients with radio-contrast-induced acute renal injury. Can intravenous sodium-bicarbonate improve long-term outcomes?

BACKGROUND/PURPOSE

Radiocontrast-induced acute kidney injury (RAKI) is a frequent complication during angiography and is associated with adverse prognosis. Most of the studies evaluating the long-term outcome of patients with RAKI are based on institutional registries. This is the first prospective study to evaluate the 5-year outcomes of patients with RAKI, and assess the effect of sodium bicarbonate (SB) in the long-term outcomes of patients with chronic kidney disease (CKD) undergoing non-emergent coronary angiography.

MATERIALS/METHODS

382 CKD stage III-IV patients undergoing elective non-emergent coronary angiography were randomized to SB (n = 192) or normal saline (NS) solution (n = 190). Incidence of RAKI, in-hospital, 1- and 5-year mortality and renal replacement therapy (RRT), and 5-year major adverse renal and cardiovascular events (MARCE) were compared between groups. Outcomes of patient with and without RAKI were compared after five-years of prospective follow-up. Multivariate predictors of RAKI and death at 5-years were determined.

RESULTS

The use of SB did not improve the incidence of RAKI, in-hospital outcomes, survival, and freedom from RRT or MARCE after 5-years of follow-up. Patients that developed RAKI had a significantly higher mortality at 1-year [8.9% Vs. 1.2%] and 5-years (36% Vs. 11%) (P < 0.01).

CONCLUSIONS

Hydration with SB showed no benefit compared to NS in preventing RAKI. The use of SB was not superior to NS after 5-years of follow-up regarding MARCE, survival or freedom of RRT. Five-year mortality among patients who developed RAKI remains high, and further research is needed to find the best preventive strategy for this high-risk group of patients.

SUMMARY

Radiocontrast-induced acute-kidney-injury (RAKI) is associated with poor long-term outcomes in observational and short-term studies. Hydration with sodium bicarbonate (SB) had been evaluated in the prevention of RAKI; but its long-term effect has not been evaluated. We randomized 382 high high-risk patients undergoing coronary angiography to SB or normal saline following them for five years. SB showed no benefit in preventing RAKI, decreasing major adverse renal and cardiovascular events, improving survival or freedom from dialysis after 5-years. This is the first study to follow patients with RAKI for a period of 5-years, showing a significantly higher mortality in this group of patients.

Feasibility of coronary fractional flow reserve with dual anti-platelet therapy in low risk coronary lesions without systemic anticoagulation-results of the SMART-FFR study

BACKGROUND

Fractional flow reserve (FFR) is used to assess the functional significance of coronary artery stenoses. The optimal anti-thrombotic regimen for FFR has not been studied.

PURPOSE

The goal of this study was to determine whether FFR could be safely performed in Type A coronary lesions, using only upstream dual anti-platelet therapy (DAT) with aspirin and clopidogrel, compared with DAT plus anticoagulation in low risk coronary lesions.

METHODS/MATERIALS

Two hundred patients undergoing FFR for Type A intermediate coronary lesions were blindly randomized into two groups of 100 patients each. Group 1: Upstream DAT, without intra-procedural anti-coagulation and Group 2: Upstream DAT plus intra-procedural bivalirudin. The primary end-points were any coronary thrombotic complications during the index hospital stay, and a composite end-point of any major adverse cardiovascular events (MACE) at 30-days. Secondary end-points included post-procedure troponin levels and TIMI major and minor bleeding scores.

RESULTS

There were no thrombotic complications reported. At 30-days, two MACE occurred in Group 1, and three in Group 2 (p=0.83). No difference was seen in the post-procedure troponin levels (p=0.72), or TIMI bleeding scores study between groups (p=093).

CONCLUSIONS

This initial study evaluating a simplified anti-thrombotic regimen for FFR, suggests that FFR can be performed in low risk coronary lesions using DAT without the need for intra-procedural anticoagulation, with similar results as DAT plus anticoagulation with bivalirudin. Further research in this area is needed to determine the optimal and most cost-effective anti-thrombotic regimen for FFR calculation.

Arterial blood pressure and cardiovascular responses to yoga practice

CONTEXT

Yoga is qualitatively different from any other mode of physical activity in that it consists of a unique combination of isometric muscular contractions, stretching exercises, relaxation techniques, and breathing exercises. In particular, yoga postures consist of systemic isometric contractions that are known to elicit marked increases in mean blood pressure that are not observed during dynamic exercise. Stretching can also induce increases in blood pressure and sympathetic nerve activity in the muscles. Currently, not much is known about changes in blood pressure and other cardiovascular responses to yoga practice.

OBJECTIVE

The study intended to determine the acute effects of one session of hatha yoga practice on blood pressure and other cardiovascular responses. To gain insight into the long-term effects of yoga practice, both novice (n = 19) and advanced (n = 18) yoga practitioners were studied.

DESIGN

The two groups were matched for age, gender, BMI, and blood pressure.

SETTING

The setting was a research laboratory at a university.

PARTICIPANTS

Thirty-six apparently healthy, nonobese, sedentary, or recreationally active individuals from the community participated in the study. Intervention The intervention comprised one session of yoga practice, in which participants followed a custom made instructional video providing a yoga routine that consisted of a series of 23 hatha-based yoga postures.

OUTCOME MEASURES

Prior to arriving at the laboratory, each participant completed a research health questionnaire, a training-status questionnaire, and a yoga-experience questionnaire. Prior to the yoga practice, each participant's height, body fat percentage, trunk or lumbar flexibility, and arterial stiffness as assessed by carotid femoral pulse wave velocity (cfPWV) were measured. For each posture during the yoga practice, the study continuously measured systolic, mean, and diastolic blood pressures, heart rate, stroke volume, and cardiac output.

RESULTS

Systolic, mean, and diastolic blood pressures increased significantly during the yoga practice. The magnitude of these increases in blood pressure was greatest with standing postures. Heart rate and cardiac output increased significantly during yoga practice, especially with standing postures. Overall, no differences existed in cardiovascular responses between the novice and advanced practitioners throughout the yoga testing session; cfPWV velocity was significantly and inversely associated with lumbar flexion but not with sit-and-reach test scores.

CONCLUSIONS

The research team concluded that a variety of hatha yoga postures, especially standing postures, evoked significant increases in blood pressure. The elevation in blood pressure due to yoga practice was associated with increases in cardiac output and heart rate, which are responses similar to those observed in isometric exercise. The lack of obvious differences in blood pressure and other cardiovascular responses between novice and advanced yoga practitioners suggests that long-term yoga practice does not attenuate acute yoga responses.

Effects of swimming training on blood pressure and vascular function in adults >50 years of age

Swimming is ideal for older adults because it includes minimum weight-bearing stress and decreased heat load. However, there is very little information available concerning the effects of regular swimming exercise on vascular risks. We determined if regular swimming exercise would decrease arterial blood pressure (BP) and improve vascular function. Forty-three otherwise healthy adults >50 years old (60 ± 2) with prehypertension or stage 1 hypertension and not on any medication were randomly assigned to 12 weeks of swimming exercise or attention time controls. Before the intervention period there were no significant differences in any of the variables between groups. Body mass, adiposity, and plasma concentrations of glucose and cholesterol did not change in either group throughout the intervention period. Casual systolic BP decreased significantly from 131 ± 3 to 122 ± 4 mm Hg in the swimming training group. Significant decreases in systolic BP were also observed in ambulatory (daytime) and central (carotid) BP measurements. Swimming exercise produced a 21% increase in carotid artery compliance (p <0.05). Flow-mediated dilation and cardiovagal baroreflex sensitivity improved after the swim training program (p <0.05). There were no significant changes in any measurements in the control group that performed gentle relaxation exercises. In conclusion, swimming exercise elicits hypotensive effects and improvements in vascular function in previously sedentary older adults.

Endothelial ischemia-reperfusion injury in humans: association with age and habitual exercise

Advancing age is a major risk factor for coronary artery disease. Endothelial dysfunction accompanied by increased oxidative stress and inflammation with aging may predispose older arteries to greater ischemia-reperfusion (I/R) injury. Because coronary artery ischemia cannot be induced safely, the effects of age and habitual endurance exercise on endothelial I/R injury have not been determined in humans. Using the brachial artery as a surrogate model of the coronary arteries, endothelial function, assessed by brachial artery flow-mediated dilation (FMD), was measured before and after 20 min of continuous forearm occlusion in young sedentary (n = 10, 24 ± 2 yr) and middle-aged (n = 9, 48 ± 2 yr) sedentary adults to gain insight into the effects of primary aging on endothelial I/R injury. Young (n = 9, 25 ± 1 yr) and middle-aged endurance-trained (n = 9, 50 ± 2 yr) adults were also studied to determine whether habitual exercise provides protection from I/R injury. Fifteen minutes after ischemic injury, FMD decreased significantly by 37% in young sedentary, 35% in young endurance-trained, 68% in middle-aged sedentary, and 50% in middle-aged endurance-trained subjects. FMD returned to baseline levels within 30 min in young sedentary and endurance-trained subjects but remained depressed in middle-aged sedentary and endurance-trained subjects. Circulating markers of antioxidant capacity and inflammation were not related to FMD. In conclusion, advancing age is associated with a greater magnitude and delayed recovery from endothelial I/R injury in humans. Habitual endurance exercise may provide partial protection to the endothelium against this form of I/R injury with advancing age.

Laplace barriers for electrowetting thresholding and virtual fluid confinement

Reported are Laplace barriers consisting of arrayed posts or ridges that impart ∼100 to 1000 s of N/m(2) Laplace pressure for fluid confinement, but the Laplace pressure is also small enough such that the barriers are porous to electrowetting control. As a result, the barriers are able to provide electrowetting flow thresholding and virtual fluid confinement in noncircular fluid geometries. A simple theoretical model for the barriers and experimental demonstrations validate functionality that may be useful for lab-on-chip, display devices, and passive matrix control, to name a few applications.

Arterial stiffening following eccentric exercise-induced muscle damage

Acute inflammatory responses are linked to a transient increase in risk of a cardiovascular event, and this risk may be mediated by a concomitant reduction in vascular function. Humans experience an acute inflammatory response as a consequence of infection, injury, or muscle damage. We measured macrovascular function before and after eccentric exercise to determine whether muscle damage from unaccustomed exercise has an unfavorable effect on the large elastic arteries. A total of 27 healthy sedentary or recreationally active men (age 18–38 years) participated in either bilateral leg press eccentric exercise or unilateral elbow flexor eccentric exercise. Postexercise muscle damage was confirmed by significant reductions in isometric strength and increases in muscle soreness ( P < 0.05). Carotid-femoral pulse-wave velocity was significantly elevated 48 h after leg exercise (808 ± 31 vs. 785 ± 30 cm/s; P < 0.05) and arm exercise (790 ± 28 vs. 755 ± 24 cm/s; P < 0.05). There were no changes in mean arterial pressure. C-reactive protein was elevated after leg exercise but not after arm exercise. The increase in carotid-femoral pulse wave velocity 48 h after arm exercise was associated with muscle strength ( r = −0.47; P < 0.05) and creatine kinase concentrations ( r = 0.70; P < 0.01). We concluded that eccentric exercise in both small and large muscle mass translates to transient, unfavorable changes in central macrovascular function and that the increase in central arterial stiffness after small muscle eccentric exercise is associated with indicators of muscle damage.

Interrelationships among noninvasive measures of postischemic macro- and microvascular reactivity

The clinical importance of vascular reactivity as an early marker of atherosclerosis has been well established, and a number of established and emerging techniques have been employed to provide measurements of peripheral vascular reactivity. However, relations between these methodologies are unclear as each technique evaluates different physiological aspects related to micro- and macrovascular reactive hyperemia. To address this question, a total of 40 apparently healthy normotensive adults, 19-68 yr old, underwent 5 min of forearm suprasystolic cuff-induced ischemia followed by postischemic measurements. Measurements of vascular reactivity included 1) flow-mediated dilatation (FMD), 2) changes in pulse wave velocity between the brachial and radial artery (DeltaPWV), 3) hyperemic shear stress, 4) reactive hyperemic flow, 5) reactive hyperemia index (RHI) assessed by fingertip arterial tonometry, 6) fingertip temperature rebound (TR), and 7) skin reactive hyperemia. FMD was significantly and positively associated with RHI (r=0.47) and TR (r=0.45) (both P<0.01) but not with reactive hyperemic flow or hyperemic shear stress. There was no correlation between two measures of macrovascular reactivity (FMD and DeltaPWV). Skin reactive hyperemia was significantly associated with RHI (r=0.55) and reactive hyperemic flow (r=0.35) (both P<0.05). There was a significant association between reactive hyperemia and RHI (r=0.30; P<0.05). In more than 75% of cases, vascular reactivity measures were not significantly associated. We concluded that associations among different measures of peripheral micro- and macrovascular reactivity were modest at best. These results suggest that different physiological mechanisms may be involved in changing different measures of vascular reactivity.

Drug-eluting stents: new era and new concerns

At present there is much excitement about drug-eluting stents, which hold promise for the treatment of coronary artery disease. This ingenious therapy involves coating the outside of a standard coronary stent with a thin polymer containing medication that can prevent scarring at the site of coronary intervention. Early trials with sirolimus coated stents showed that they might prevent coronary artery restenosis, but later studies, involving more complex coronary lesions, did not show a complete absence of restenosis. Recent studies have demonstrated the long term cost effectiveness of drug-eluting stents as they have reduced the need for revascularisation procedures. At present there are few data on the safety and effectiveness of stents over follow up periods exceeding two years, and data obtained from animal models of stenting might not be completely applicable to humans. There are concerns that drug-eluting stents might delay, rather than inhibit, restenosis. Also there is concern regarding the inflammation caused by the polymer substrate. This article reviews the present data on drug-eluting stents and their benefits, shortcomings, and concerns.

Insulin resistance, insulin sensitization and inflammation in polycystic ovarian syndrome

It is estimated that 5-10% of women of reproductive age have polycystic ovarian syndrome (PCOS). While insulin resistance is not part of the diagnostic criteria for PCOS, its importance in the pathogenesis of PCOS cannot be denied. PCOS is associated with insulin resistance independent of total or fat-free body mass. Post-receptor defects in the action of insulin have been described in PCOS which are similar to those found in obesity and type 2 diabetes. Treatment with insulin sensitizers, metformin and thiazolidinediones, improve both metabolic and hormonal patterns and also improve ovulation in PCOS. Recent studies have shown that PCOS women have higher circulating levels of inflammatory mediators like C-reactive protein, tumour necrosis factor-alpha, tissue plasminogen activator and plasminogen activator inhibitor-1 (PAI-1). It is possible that the beneficial effect of insulin sensitizers in PCOS may be partly due to a decrease in inflammation.

Imaging of the vulnerable plaque: new modalities

Atherosclerosis is currently considered to be an inflammatory and thus a systemic disease affecting multiple arterial beds. Recent advances in intravascular imaging have shown multiple sites of atherosclerotic changes in coronary arterial wall. Traditionally, angiography has been used to detect and characterize atherosclerotic plaque in coronary arteries, but recently it has been found that plaques that are not significantly stenotic on angiography cause acute myocardial infarction. As a result, newer imaging and diagnostic modalities are required to predict which of the atherosclerotic plaque are prone to rupture and hence distinguish "stable" and "vulnerable" plaques. Intravascular ultrasound can identify multiple plaques that are not seen on coronary angiography. Thermography has shown much promise and is based on the concept that the inflammatory plaques are associated with increased temperature and can also identify "vulnerable patients." Of all these newer modalities, magnetic resonance imaging has shown the most promise in identification and characterization of vulnerable plaques. In this article, we review the newer coronary artery imaging modalities and discuss the limitations of traditional coronary angiography.