Baseline cardiovascular risk in the INSIGHT Strategic Timing of AntiRetroviral Treatment (START) trial

OBJECTIVES

The Strategic Timing of AntiRetroviral Treatment (START) trial has recruited antiretroviral-naïve individuals with high CD4 cell counts from all regions of the world. We describe the distribution of cardiovascular disease (CVD) risk factors, overall and by geographical region, at study baseline.

METHODS

The distribution of CVD risk factors was assessed and compared by geographical region among START participants who had a baseline electrocardiogram (n = 4019; North America, 11%; Europe/Australia/Israel, 36%; South America, 26%; Asia, 4%; Africa, 23%; median age 36 years; 26% female).

RESULTS

About 58.3% (n = 2344) of the participants had at least one CVD risk factor and 18.9% (n = 761) had two or more. The most common CVD risk factors were current smoking (32%), hypertension (19.3%) and obesity (16.5%). There were significant differences in the prevalence of CVD risk factors among geographical regions. The prevalence of at least one risk factor across regions was as follows: North America, 70.0%; Europe/Australia/Israel, 65.1%; South America, 49.4%; Asia, 37.0%; Africa, 55.8% (P-value < 0.001). Significant regional differences were also observed when risk factors were used as part of the Framingham and Data Collection on Adverse events of Anti-HIV Drugs (D:A:D) risk scores or used to define a favourable risk profile.

CONCLUSIONS

CVD risk factors are common among START participants, and their distribution varies by geographical region. Better understanding of how and why CVD risk factors develop in people with HIV infection and their geographical distributions could shed light on appropriate strategies for CVD prevention and may inform the interpretation of the results of START, as CVD is expected to be a major fraction of the primary endpoints observed.

Acute renal failure: clinical aspects and pathophysiology

Acute renal failure may be caused by multiple conditions including those which are due to some direct hemodynamic or nephrotoxic insult. In considering the pathophysiology of these entities, it seems appropriate to differentiate between the initiating and the maintenance phase of the disorder. In the former, renal ischemia and/or a direct effect of a given nephrotoxic agent seems to be the basis for the underlying renal damage. In the maintenance phase, renal functional impairment is maintained by a number of factors which include persistent renal vasoconstriction, tubular obstruction, a leakage of filtrate across damaged tubular epithelium, and a reduction in glomerular capillary permeability. The therapy and possible preventive aspects of these entities are discussed.

Effect of statin therapy in reducing the risk of serious non-AIDS-defining events and nonaccidental death

BACKGROUND

Excessive inflammation persists despite antiretroviral treatment. Statins decrease cardiovascular (CV) disease risk by reducing low-density lipoprotein cholesterol and inflammation. We performed an exploratory analysis to evaluate whether statin therapy decreased risk of non-AIDS-defining events and nonaccidental death.

METHODS

A total of 3601 subjects not on a statin from the AIDS Clinical Trials Group Longitudinal Linked Randomized Trials cohort were included. Outcome was time to first clinical event (CV event, renal or hepatic disease, incident diabetes, thrombotic/embolic event, nontraumatic fracture, non-AIDS-defining malignancy, serious bacterial infection, or nonaccidental death); event categories were also analyzed separately. Inverse probability of treatment and censoring weighted Cox proportional hazard models were used to assess the causal statin effect. Differential statin effects by baseline covariates were evaluated.

RESULTS

Over 15 135 person-years (PY) of follow-up, 484 subjects initiated statins; 616 experienced an event (crude event rate, 4.4/100 PY on a statin and 4.1/100 PY not on a statin); the unadjusted hazard ratio (HR) was 1.17 (95% confidence interval [CI], .91-1.50). In a final weighted model, the adjusted HR (AHR) was 0.81 (95% CI, .53- 1.24). Results for other clinical events were similar, except for malignancies (AHR, 0.43 [95% CI, .19-.94]) and bacterial infections (AHR, 1.30 [95% CI, .64-2.65]). No differential statin effects by baseline covariates were detected.

CONCLUSIONS

Although statin therapy was not associated with a reduction in time to all non-AIDS-defining event or nonaccidental death, it was associated with a statistically significant 57% reduction in non-AIDS-defining malignancies. Confirmatory studies are needed to evaluate statin-associated reduction in risk of cancer and non-AIDS-associated morbidities.

Transient effusive-constrictive pericarditis due to chemotherapy

Commonly used chemotherapeutic agents, specifically cytarabine and daunorubicin, can cause effusive-constrictive pericarditis. We describe a case of transient effusive-constrictive pericarditis in a patient with acute myelogenous leukemia. This is the first case report of a patient with transient effusive-constrictive pericarditis due to chemotherapy.

Transesophageal echocardiography for the evaluation and management of patients with cerebral ischemia

To prevent recurrent strokes and transient ischemic attacks, considerable attention is devoted to investigating the etiology of acute cerebral ischemia in the large subpopulation of patients without an easily identifiable cause. In general, transthoracic echocardiography is an insensitive tool for the evaluation of patients with cerebral ischemia, unless clinical signs and/or symptoms of cardiac disease are present. Transesophageal echocardiography (TEE), because of its increased sensitivity for aortic arch atheromata, atrial septal pathology, left atrial thrombi, and valvular abnormalities, is the preferred cardiac imaging modality, especially in young patients, older patients with hypertension or systemic atherosclerosis, and patients with prosthetic heart valves. This paper reviews the prognostic and therapeutic impact of TEE in patients with cerebral ischemia, specifically focusing on the ability of information obtained by this technique to alter patient management and improve risk stratification.

Improved risk stratification in unstable angina: identification of patients at low risk for in-hospital cardiac events by admission echocardiography

BACKGROUND

Current protocols for risk stratification of patients with acute chest pain syndromes rely on clinical parameters and are oriented toward identification of patients at high risk for adverse cardiac events; however, this paradigm for risk stratification does not adequately address the observation that adverse cardiac events are relatively uncommon in this population. In an era of cost containment, consideration also should be given to identification of patients at low risk for adverse cardiac events, who may be safely discharged without expensive inpatient hospitalization.

HYPOTHESIS

The purpose of this study was to develop echocardiographic predictors that identify unstable angina patients at low risk for adverse cardiac events and that discriminate between low- and high-risk patients.

METHODS

The predictive accuracy of retrospectively determined echocardiographic predictors were compared in a population-based sample of 66 consecutive unstable angina patients undergoing echocardiography within 24 h of admission.

RESULTS

Echocardiographic predictors of adverse events included wall motion score index > or = 0.2, ejection fraction < or = 40%, and mitral regurgitation severity > 2. One or more echocardiographic predictors of adverse events were present in 32 patients (48%). A composite echocardiographic predictor of adverse events was specific, had a high positive predictive value for the identification of high-risk patients, and discriminated between unstable angina patients at high and low risk for adverse cardiac events.

CONCLUSION

Echocardiographic predictors of adverse events are specific and discriminate between unstable angina patients at high and low risk for adverse cardiac events.

Putting the Diabetes Prevention Program into practice: a program for weight loss and cardiovascular risk reduction for patients with metabolic syndrome or type 2 diabetes mellitus

BACKGROUND

The increasing incidence and prevalence of metabolic syndrome and type 2 diabetes mellitus (DM) have significant implications on health world-wide. Large clinical trials have demonstrated the effectiveness of a comprehensive lifestyle program with a goal of moderate weight loss (5-7%) and regular exercise (150 minutes/week), resulting in a significant decrease in the incidence of type 2 DM and cardiovascular risk.

METHODS

This study reports on the translation of the multi-center Diabetes Prevention Program (DPP) into a cardiac rehabilitation program, utilizing the expertise and experience of a cardiac rehabilitation program staff. The study adapted materials from the DPP to develop a program that fit local needs for diabetes prevention.

RESULTS

Most participants completed the program (11 months) and their moderate weight loss was maintained for 11-12 months. At 11-12 months, waist circumference was reduced by approximately 2 inches, percent body fat was reduced by 5% (11% relative decrease, p<.05), weight was decreased by 10.1 pounds (p<.05), and blood pressure was reduced 8/3 mm Hg (p<.05). Exercise, nutrition, glucose, triglycerides, LDL-cholesterol and HDL cholesterol were all were significantly improved at 11-12 months (p<.05).

CONCLUSIONS

Efforts to improve lifestyle and reduce body weight are important to patients at risk of developing diabetes. This program demonstrates that an intensive effort can significantly improve lifestyle and reduce body weight in patients with DM or at risk for DM. A program that simulates cardiac rehabilitation, translated from a successful clinical trial into practice, resulted in significant reduction and improvement in metabolic outcomes and cardiovascular risk. Support for cardiac rehabilitation from insurers to develop similar programs is encouraged and deserves further study.

The effects of lipid-lowering and antioxidant vitamin therapies on flow-mediated vasodilation of the brachial artery in older adults with hypercholesterolemia

OBJECTIVES

The goal of this study was to determine the long-term effects of statins and antioxidant vitamins on flow-mediated vasodilation of the brachial artery in older adults with hypercholesterolemia.

BACKGROUND

Lipid-lowering therapy and antioxidant vitamins improve endothelium-dependent vasodilation in young and middle-aged adults with hypercholesterolemia, but their effects in older adults are not known.

METHODS

Two double-blind, placebo-controlled studies were performed in individuals > or =70 years old with low-density lipoprotein cholesterol (LDL-C) > or =140 mg/dl. In the first study, 37 subjects were randomized to receive (group 1) pravastatin for six months then pravastatin and vitamin E for six additional months or (group 2) vitamin E for six months, then pravastatin and vitamin E for six additional months. In the second study, additional 17 subjects sequentially received simvastatin for six months, then simvastatin and vitamins C and E for six additional months. Flow-mediated vasodilation of the brachial artery was measured by high-resolution ultrasound.

RESULTS

At baseline, subjects in both studies were similar in age (mean +/- SD, 75.8 +/- 4.2 years), gender, systolic blood pressure, total cholesterol (261.6 +/- 37.4 mg/dl), LDL-C (180.3 +/- 28.1 mg/dl), high-density lipoprotein cholesterol and triglycerides levels. Flow-mediated vasodilation was severely impaired (2.2 +/- 3.9%). Both statins reduced total and LDL-C levels (p < 0.001); however, neither statin, antioxidant vitamin regimen nor the combination of statins and antioxidant vitamins improved flow-mediated vasodilation of the brachial artery. At baseline, nitroglycerin-mediated vasodilation also was impaired (10.7 +/- 5.6%) and did not change in either study.

CONCLUSIONS

Older adults with hypercholesterolemia have impaired flow-mediated vasodilation of the brachial artery that does not improve after one year of therapy with statins and antioxidant vitamins, despite significant lipid-lowering.

Use of human immunodeficiency virus-1 protease inhibitors is associated with atherogenic lipoprotein changes and endothelial dysfunction

BACKGROUND

Human immunodeficiency virus protease inhibitors (HIV PIs) are associated with hyperlipidemia, hyperglycemia, and obesity; however, it is not known whether they increase risk of atherosclerotic vascular disease. The purposes of this study were to characterize the lipoprotein abnormalities associated with use of HIV PIs in individuals with HIV infection and to determine the pathophysiological significance of these changes by assessing their effect on endothelial dysfunction.

METHODS AND RESULTS

This was a cross-sectional study of 37 adults with HIV-1 infection who were receiving antiretroviral therapy. Twenty-two were taking HIV PIs (group 1); 15 were not (group 2). Lipids and lipoproteins were measured by enzymatic techniques and nuclear magnetic resonance spectroscopic analysis. Flow-mediated vasodilation (FMD) of the brachial artery was measured by high-resolution ultrasound. Subjects in both groups were similar in regard to age, time since diagnosis of HIV infection, and CD4 cell count. Group 1 subjects had higher total cholesterol (5.68 versus 4.42 mmol/L, P=0.007) and triglyceride (4.43 versus 1.98 mmol/L, P=0.009) levels, characterized by elevated levels of IDL and VLDL. Subjects in group 1 had impaired FMD (2.6+/-4.6%), indicative of significant endothelial dysfunction. Group 2 subjects had normal FMD (8.1+/-6.7%, P=0.005). In group 1, chylomicron, VLDL, IDL, and HDL cholesterol levels predicted FMD.

CONCLUSIONS

Use of HIV PIs is associated with atherogenic lipoprotein changes and endothelial dysfunction. Because these metabolic and vascular changes predispose to atherosclerosis, monitoring and treatment of dyslipidemia in patients taking these medications is warranted.

Managing dyslipidemia in older adults

OBJECTIVES

To summarize and critically review clinical trial data regarding dyslipidemia as a risk factor for coronary heart disease (CHD) and the efficacy and safety of lipid-lowering interventions in older adults. Based on these data, clinical recommendations for diagnosing and managing dyslipidemia in older adults are provided.

METHODS

Peer-reviewed journal articles were identified by a MEDLINE search and a review of journal article references. Studies that were performed exclusively in subjects older than 65 years or that included a large subgroup of older adults were included.

CONCLUSIONS

Elevated low density lipoprotein and total cholesterol levels are independent risk factors for CHD events in patients aged older than 65 years. Older adults have a higher risk of mortality attributable to hypercholesterolemia. Diet and lipid-lowering medications safely and effectively lower cholesterol levels in this age group. Exercise increases high-density lipoprotein cholesterol levels and decreases triglyceride levels. If accompanied by weight loss, exercise may reduce low-density lipoprotein and total cholesterol levels. Improving lipid levels in older adults with CHD decreases the risk of future coronary events by up to 45%, and significant effects on outcome measures may be observed within 2 years of the initiation of therapy.

Gender differences in acute myocardial infarction: the University of Wisconsin experience

OBJECTIVE

To investigate gender differences in baseline characteristics, presentation, and treatment of patients with acute myocardial infarction (MI) admitted to the University of Wisconsin Hospital Coronary Care Unit (CCU) over a 1-year period.

METHODS

A retrospective review was performed on the charts of all patients (n = 293) admitted to the CCU in 1996 with a discharge diagnosis of acute MI. In 83 women and 187 men with analyzable data (n = 270), 42 factors related to baseline characteristics, presentation, treatment, and outcomes were identified and analyzed for gender differences.

RESULTS

On average, women were 5 years older than men (p < .01). By univariate comparison, women were less likely than men to be smokers (p < .001); more likely to have underlying hypertension (p < .01), diabetes mellitus (p < 0.05), non-Q-wave infarctions (p < .01), and congestive heart failure (CHF, p < .05); and more likely to have received diuretics (p < .001) and ACE inhibitors (p < .01). While women were less likely than men to undergo coronary angiography (p < .05) and more likely to have echocardiograms (p < 0.05), rates of coronary artery bypass graft surgery, angioplasty, and the use of thrombolytics were similar for men and women. Clinical outcomes were similar in both groups. CHF, hypertension, and use of ACE inhibitors remained the only significant gender differences when data were adjusted for age.

CONCLUSION

Comparing men and women with acute MI at UW Hospital revealed some differences in clinical characteristics and management. Except for CHF, hypertension, and use of ACE inhibitors (all of which may be related), these differences disappeared when the data were adjusted for age. This is particularly notable for the disappearance of the difference in the use of coronary angiography between men and women. The comparable use of beta-blockers, aspirin, and nitrates, and the similar clinical outcomes in men and women, suggest less gender difference in MI management at UW Hospital than reported in other studies.

Aab Institute of Biomedical Sciences

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Purple grape juice improves endothelial function and reduces the susceptibility of LDL cholesterol to oxidation in patients with coronary artery disease

BACKGROUND

In vitro, the flavonoid components of red wine and purple grape juice are powerful antioxidants that induce endothelium-dependent vasodilation of vascular rings derived from rat aortas and human coronary arteries. Although improved endothelial function and inhibition of LDL oxidation may be potential mechanisms by which red wine and flavonoids reduce cardiovascular risk, the in vivo effects of grape products on endothelial function and LDL oxidation have not been investigated. This study assessed the effects of ingesting purple grape juice on endothelial function and LDL susceptibility to oxidation in patients with coronary artery disease (CAD).

METHODS AND RESULTS

Fifteen adults with angiographically documented CAD ingested 7.7+/-1.2 mL. kg(-1). d(-1) of purple grape juice for 14 days. Flow-mediated vasodilation (FMD) was measured using high-resolution brachial artery ultrasonography. Susceptibility of LDL particles to oxidation was determined from the rate of conjugated diene formation after exposure to copper chloride. At baseline, FMD was impaired (2.2+/-2. 9%). After ingestion of grape juice, FMD increased to 6.4+/-4.7% (P=0.003). In a linear regression model that included age, artery diameter, lipid values, and use of lipid-lowering and antioxidant therapies, the effect of grape juice on FMD remained significant (mean change 4.2+/-4.4%, P<0.001). After ingestion of grape juice, lag time increased by 34.5% (P=0.015).

CONCLUSIONS

Short-term ingestion of purple grape juice improves FMD and reduces LDL susceptibility to oxidation in CAD patients. Improved endothelium-dependent vasodilation and prevention of LDL oxidation are potential mechanisms by which flavonoids in purple grape products may prevent cardiovascular events, independent of alcohol content.

Hyperhomocysteinemia and atherosclerotic vascular disease: pathophysiology, screening, and treatment. off

Hyperhomocysteinemia has recently been identified as an important risk factor for atherosclerotic vascular disease. This article reviews homocysteine metabolism, causes of hyperhomocysteinemia, the pathophysiological findings of this disorder, and epidemiological studies of homocysteine and vascular disease. Screening for hyperhomocysteinemia should be considered for patients at high risk for vascular disease or abnormalities of homocysteine metabolism. For primary prevention of vascular disease, treatment of patients with homocysteine levels of 14 micromol/L or higher should be considered. For secondary prevention, treatment of patients with homocysteine levels of 11 micromol/L or higher should be considered. Treatment is most conveniently administered as a folic acid supplement (400-1000 microg) and a high-potency multivitamin that contains at least 400 microg of folate. Higher doses of folic acid and cyanocobalamin supplements may be required in some patients. Until prospective clinical trial data become available, these conservative recommendations provide a safe, effective, and evidence-based approach to the diagnosis, evaluation, and management of patients with hyperhomocysteinemia.

Treatment of severe hypertriglyceridemia lowers plasma viscosity

Elevated plasma viscosity is a predictor of atherosclerotic vascular disease and is a potential mechanism by which hypertriglyceridemia increases cardiovascular risk. Previous studies of plasma viscosity reduction in hypertriglyceridemic patients used medications that lowered both triglyceride and fibrinogen levels. Because fibrinogen is a major determinant of viscosity, it is unclear whether triglyceride reduction alone is sufficient to reduce plasma viscosity. The purpose of this study was to determine whether triglyceride-lowering therapy reduces plasma viscosity. This was a prospective study of 24 adult patients with severe hypertriglyceridemia (> or = 5.67 mmol/l). Fasting lipid, total serum protein, fibrinogen, plasma viscosity and serum viscosity levels were measured before and after therapy with 1200 mg/d of gemfibrozil. Triglyceride levels decreased by 70% (P < 0.001). Mean plasma and serum viscosity levels decreased by 0.082 mPa/s (P = 0.003) and 0.086 mPa/s (P = 0.013), respectively. Fibrinogen levels did not change significantly. Triglyceride-lowering therapy reduced plasma and serum viscosity without changes in fibrinogen levels. Since serum samples are deplete of fibrinogen, the serum viscosity reduction observed is corroborative evidence for an independent effect of triglyceride-lowering therapy on plasma viscosity. This observation provides a physiological rationale for triglyceride-lowering therapy in patients at risk for atherosclerotic vascular disease, the chylomicronemia syndrome and pancreatitis.

Comparison of estimates of right atrial pressure by physical examination and echocardiography in patients with congestive heart failure and reasons for discrepancies

Clinical estimates of right atrial pressure from the jugular venous pulse were accurate when right atrial pressure was normal, but systematically underestimated elevated right atrial pressures. Because the increased distance from the mid-right atrium to the sternal angle is not accounted for, apparently normal right atrial pressure estimates by this technique do not reliably exclude elevated right atrial pressure in patients with congestive heart failure.

Echocardiography for hemodynamic assessment of patients with advanced heart failure and potential heart transplant recipients

OBJECTIVES

This study sought to assess the accuracy of Doppler echocardiographic techniques for the determination of right heart catheterization hemodynamic variables in patients with advanced heart failure and in potential heart transplant recipients.

BACKGROUND

Doppler echocardiographic techniques permit the noninvasive acquisition of hemodynamic variables traditionally used for the assessment of patients with advanced heart failure and potential heart transplant candidates. However, the accuracy of these techniques has not been sufficiently well documented for clinical application in individual patients.

METHODS

Echocardiographic data required for estimation of mean right atrial, pulmonary artery and mean left atrial pressures and cardiac output were obtained. Right heart catheterization was performed immediately after Doppler echocardiographic data were acquired, before any intervention that might have altered the subject's hemodynamic status.

RESULTS

A complete Doppler echocardiographic hemodynamic data set was acquired in 21 (84%) of 25 subjects. For all variables, invasive and noninvasive hemodynamic values were highly correlated (p < 0.001), with minimal bias and narrow 95% confidence limits. An algorithm constructed from the noninvasive hemodynamic variable values identified all patients with adverse pulmonary vascular hemodynamic variables (i.e., transpulmonary gradient > or = 12 mm Hg, pulmonary vascular resistance > or = 3 Wood units or pulmonary vascular resistance index > or = 6 Wood units x m2). This algorithm identified 12 (71%) of 19 patients for whom right heart catheterization was unnecessary.

CONCLUSIONS

Doppler echocardiographic estimates of hemodynamic variables in patients with advanced heart failure are accurate and reproducible. This noninvasive methodology may assist with monitoring and optimization of medical therapy in patients with advanced heart failure and may obviate the need for routine right heart catheterization in potential heart transplant candidates.

Homocysteine: a new risk factor for atherosclerosis

The accumulating evidence for the role of homocysteine as a risk factor for atherosclerosis is persuasive. A high plasma homocysteine concentration induces pathologic changes in the arterial wall and thus is strongly associated with an increased risk of atherosclerosis, manifested as cardiovascular, cerebrovascular and peripheral vascular events. Studies are being conducted to determine whether lowering homocysteine levels prevents occlusive events. At present, testing for elevated homocysteine concentrations should be considered in patients with premature atherosclerosis or a strong family history of atherosclerosis, since hyperhomocysteinemia is a common risk factor in these patients. Treatment of hyperhomocysteinemia is straightforward and associated with minimal risk. This disorder is usually correctable with vitamin supplements containing folic acid.

Lipoprotein Lp(a) excess and coronary heart disease

Lipoprotein Lp(a) excess has been identified as a powerful predictor of premature atherosclerotic vascular disease in several large, prospective studies. Lipoprotein Lp(a) levels modulate the risk of coronary heart disease in patients with hypercholesterolemia, and lipoprotein Lp(a) excess is commonly detected in men and women with premature coronary atherosclerosis. Lipoprotein Lp(a) contributes to atherothrombotic risk by multiple mechanisms that include impaired fibrinolysis, increased cholesterol deposition in the arterial wall, and enhanced oxidation of low density lipoprotein cholesterol. Although low density lipoprotein cholesterol reduction is the primary intervention in patients with lipoprotein Lp(a) excess, specific therapy to lower lipoprotein Lp(a) may be indicated for patients with premature coronary atherosclerosis, a strong family history of premature atherosclerosis, or refractory hypercholesterolemia. In consideration of the high prevalence of lipoprotein Lp(a) excess in patients with premature coronary heart disease and the intricate role of lipoprotein Lp(a) in atherothrombosis, this review provides an evidence-based approach to the screening and treatment of patients with lipoprotein Lp(a) excess.

Cost and appropriateness of radionuclide exercise stress testing by cardiologists and non-cardiologists

The hypothesis that a diagnostic evaluation performed by a generalist is less expensive than that performed by a specialist is untested. We retrospectively evaluated the indications and financial ramifications of radionuclide exercise stress testing by cardiologists and noncardiologists in 1,902 consecutive adults with normal resting electrocardiograms. Subjects completed radionuclide exercise tests for the diagnosis or management of coronary artery disease during a 14-month period. Tests were considered "indicated" or "not indicated" based on criteria determined from published reports and established practice guidelines. Savings in costs and charges were determined for a strategy of referral to a cardiologist before ordering tests. Non-cardiologists ordered more tests that were not indicated than cardiologists (69.6% vs 36.2%, chi-square = 209.07, p < 0.00001). Non-cardiologists also ordered tests that were not indicated in patients with (chi-square = 110.02, p < 0.00001) and without (chi-square = 110.02, p < 0.00001) and without (chi-square = 45.44, p < 0.00001) chest pain. Tests that were not indicated resulted in excess costs of $591,384 and excess charges of $1,082,400. Referral to a cardiologist before ordering tests could have saved $63,257 in costs and $169,800 in charges. Both cardiologists and non-cardiologists overutilized radionuclide exercise stress test; however, non-cardiologists were more likely to order tests that were not indicated. A strategy of referral to a cardiologist before ordering tests may be cost-effective in this population.

Thrombus associated with mitral valve calcification. A possible mechanism for embolic stroke

BACKGROUND

Several studies have demonstrated an association between mitral annular calcification and stroke; however, the pathophysiological explanation remains speculative.

CASE DESCRIPTIONS

We describe two patients with cerebral embolism in whom mitral valve calcification was demonstrated by transthoracic echocardiography. In both patients, transesophageal echocardiography identified a mass that appeared to be thrombus on the calcified portion of the mitral apparatus. There was no evidence of a hypercoagulable state or endocarditis in either case. Repeated transesophageal echocardiography after anticoagulation demonstrated resolution of the masses in both patients.

CONCLUSIONS

These cases support the hypothesis that thrombus formation may be a pathophysiological link between ischemic cerebral events and mitral annular calcification in some patients.

A unique left-to-right shunt characterized by multimodality cardiac imaging

We describe the first reported patient with a persistent left superior vena cava that communicates directly with the left atrium as an isolated congenital defect. She developed mitral stenosis and physiologic conditions that favored left-to-right shunting--a modified Lutembacher's syndrome. Noninvasive cardiac imaging completely elucidated her cardiac anatomy and physiology.

The saga of an academic clinician: from micropuncturist to macroadministrator

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Diabetic nephropathy

Diabetic nephropathy occurs in approximately 35% of all diabetic patients, both insulin and non-insulin dependent. It accounts for the largest proportion increase of all diseases as a cause for endstage renal disease in the United States. Certain populations, i.e., Pima Indians and Mexican and black Americans, have a higher propensity for developing diabetic nephropathy. The reasons for this increased incidence, however, are unclear. Pathophysiologically, numerous changes in vascular reactivity and renal physiology occur in early diabetes. These include increased sodium avidity, lower threshold for vasoconstriction secondary to angiotensin II and norepinephrine, a greater than 50% of normal increase in renal vasodilation following a protein meal, and loss of renal autoregulation. These differences are not seen in nondiabetic hypertensive subjects. The therapeutic approach to lower elevated arterial pressure in these patients should take these changes in physiology into account. Specifically, antihypertensive agents are preferred that have natriuretic properties and also blunt the effects of vasoconstrictors on both the vasculature and the cellular level, i.e., inhibit mesangial hypertrophy and matrix expansion, the hallmark of diabetes. Ideal agents, therefore, are angiotensin converting enzyme (ACE) inhibitors in the early stages of the disease, and certain calcium antagonists once renal insufficiency occurs. These choices are largely due to the hemodynamic, natriuretic, and anti-proteinuric effects of these agents. Good blood pressure control is essential for preservation of renal function, regardless of agents used. The ACE inhibitors and calcium antagonists of the verapamil and diltiazem groups have demonstrated superior efficacy for preservation of renal function over conventional therapy.

Acute renal failure. Lessons from pathophysiology

This discussion was selected from the weekly staff conferences in the Department of Medicine, University of California, SanFrancisco. Taken from a transcription, it has been edited by Nathan M. Bass, MD, PhD, Associate Professor of Medicine, under the direction of Lloyd H. Smith, Jr, MD, Professor of Medicine and Associate Dean in the School of Medicine.

Effect of Ringer infusion on ischemic acute renal failure: caution on interpreting the results of short-term studies

The effect of a 4.5 mL/h Ringer infusion on the recovery from a unilateral 40-min renal artery occlusion was investigated in Sprague-Dawley rats. The inulin clearance measured in the experimental kidney 24 and 48 h after the insult in control animals that did not receive the Ringer infusion was 0.14 +/- 0.10 (mean +/- SE) and 0.11 +/- 0.05 mL/min, respectively. In animals that received 24 h of Ringer infusion begun at the time of the renal artery occlusion the inulin clearance was 0.81 +/- 0.07 mL/min, a value significantly higher than either of the control groups (p less than .05). If, however, the Ringer infusion was stopped at 24 h and the inulin clearance measured at 48 h, it had decreased significantly (0.27 +/- 0.09 mL/min) and was no longer greater than the control groups. Similarly, if the infusion was continued for 48 h there was no longer a significant difference between the inulin clearance (0.37 +/- 0.11), when compared with 48 h of no infusion (0.11 +/- 0.05). The histology of the different groups corresponded with the functional data. We conclude that 24 h of Ringer infusion leads to functional and histological protection when measured at 24 h; however, if measured at 48 h, protection is no longer evident. These studies suggest that caution should be exercised in extrapolating from the results of protective maneuvers in ischemic acute renal failure investigated by short-term studies.

Grand cru versus generic: different approaches to altering the ratio of general internists to subspecialists

In the last decade internal medicine has become a less popular career choice among medical school graduates. In addition, there has been an increase in the percentage of internal medicine residents choosing subspecialty training. The factors that have led to the change in the ratio of subspecialists to general internists are discussed, and a plan is proposed that would make the practice of general internal medicine more attractive and reduce the number of subspecialty training positions in the United States.

Comparison of three commercially available antibodies for flow cytometric monitoring of P-glycoprotein expression in tumor cells

Cellular drug resistance to natural products is often due to the presence of an efflux pump which reduces intracellular drug content and chemosensitivity. A 170 kD cell surface resident P-glycoprotein is believed to act as the efflux pump. In the present report, we have compared three commercially available antibodies C-219, JSB-1, and mdr(Ab-1) for use in flow cytometric detection of P-glycoprotein positive cells. Our data show that C219 gives uniformly good results in a variety of murine and human tumor cell lines for detection of P-glycoprotein positive cells. We have also compared data of C219 stained cells analyzed in parallel on a flow cytometer equipped with a small laser (15 mW) and a large laser (5 watt) cell sorter. Data obtained on these two instruments are comparable. A staining protocol and data on dual staining of cells for DNA content by propidium iodide and P-glycoprotein expression after FITC labeling are also presented.

The natural history of diabetic nephropathy

Diabetic nephropathy is now the most common cause of ESRD in the US, and no other complication of diabetes is associated with more deaths. In addition to its impact on morbidity and mortality, it extracts a tremendous cost from the health-care economy. Prevention and better treatment of diabetic renal disease should be a high priority for both the health-care system and society at large. Ultimately, diabetic nephropathy should be preventable, but that goal can be accomplished only by the coordinated efforts between investigators, who work to uncover pathophysiologic processes and design new treatments, and clinicians, who take those findings to the patient's bedside.

Alanine protects rabbit proximal tubules against anoxic injury in vitro

Rabbit proximal tubules were incubated aerobically or subjected to anoxia for 30 min followed by 60 min of reoxygenation. The medium contained (in mM) 5 glucose, 10 butyrate, 4 lactate or alpha-ketoglutarate (alpha-KG), and 1 alanine. Anoxic tubules in this medium were severely injured and recovered poorly. If the incubation medium was supplemented with additional alanine (up to 2.5 or 5 mM), then anoxic injury was prevented almost completely. Tubules in high-alanine medium showed modest elevations of ATP during anoxia. Comparable elevations of ATP were induced in anoxic tubules incubated with 4 mM alpha-KG and 5 mM aspartate without alanine. These substrates are metabolized anaerobically in the mitochondria to yield ATP. Surprisingly, anoxic tubules with alpha-KG and aspartate showed severe injury despite elevated ATP. If 5 mM alanine was also present, then additional increments of ATP did not occur, but injury was prevented. Examination of glucose metabolism failed to provide evidence for stimulation of anaerobic fermentations by alanine. These results suggest that alanine-induced cytoprotection during anoxia occurs by mechanisms not related to ATP synthesis, and that elevated ATP in alanine-supplemented tubules may be a result and not the cause of protection. Cytoprotection by alanine was shown to last for less than or equal to 90 min of anoxia. Glycine, a structurally related amino acid, also protects anoxic proximal tubules (J. Clin. Invest. 80: 1446, 1987). The mechanisms that underlie the cytoprotective effects of alanine and glycine remain to be determined.

Incidence and results of arterial complications among 16,350 patients undergoing cardiac catheterization

A total of 16,350 patients underwent cardiac catheterization from January 1981 to December 1987. The brachial artery was used in 10,500 patients (group I), and the femoral artery was used in 5850 patients (group II). Surgical intervention for complications was necessary in 60 (0.57%) of the group I patients and in 14 (0.23%) of the group II patients. Hand ischemia in group I and bleeding in group II were the most frequent indications for operation. Procedures performed were segmental resection, vein interposition, and long bypass in group I, and simple suture and angioplasty were performed in group II. Fifty-six patients of the total of 74 underwent early repair (within 48 hours), and 18 patients underwent delayed intervention. Only one (1.7%) of the 56 patients who had early repair had a complication. Five of the 18 patients (28%) with delayed intervention suffered significant complications. Cardiac catheterization by the brachial or femoral route has a low incidence of complications. Delayed intervention is associated with high morbidity despite adequate restoration of circulation. Although there were fewer complications in the femoral group, they were far more serious with respect to life- or limb-threatening events.

High avidity monoclonal antibody to imidazole ring-opened 7-methylguanine

A hybridoma (K1A8) secreting a high affinity antibody to imidazole ring-opened 7-methylguanine (N5-methyl-N5-formyl-2,5,6-triamino-4-hydroxypyrimidine) was obtained from spleen cells of a mouse immunized with a conjugate of keyhole-limpet hemocyanin and imidazole ring-opened 7-methylguanylic acid (iro-7mGMP). The antibody recognizes the iro-7-methylguanine (iro-7mG) determinant in the BSA-iro-7mGMP conjugate, in chemically methylated, denatured DNA, and in the ring-opened 7-methylguanosine, 7-methyldeoxyguanosine and 7mGMP haptens. In the competitive ELISA of DNA-iro-7mG, 50% inhibition (I50) was observed at 4 fmol determinant per well (8 x 10(-11) M) using BSA-iro-7mGMP as the immobilized antigen. The lower limit of 7-methylguanine (7mG) detection in DNA is determined by the binding of unmodified DNA per se to the antibody. The intrinsic reaction of DNA with antibody is low; in the competitive ELISA I50 was obtained with 330 micrograms calf thymus DNA per 50 microliters well, equivalent to 4 nmol iro-7mG per mol nucleotide. The 7mG content of calf thymus DNA is 7 nmol per mol nucleotide (approximately 20 amol per micrograms DNA). The limit of detection of 7mG by competitive ELISA is quoted provisionally as 7 nmol iro-7mG per mol nucleotide, where 30% inhibition of antibody binding is obtained in the presence of 105 micrograms DNA per 50 microliters well. Nuclear DNAs of tissue culture cells treated with 0, 0.01 and 0.1 mM N-methyl-N'-nitro-N-nitrosoguanidine contained 0.18, 31 and 320 mumol, respectively, of 7-methylguanine adducts per mol of nucleotides. This report indicates that the K1A8 antibody will serve to quantify DNA alkylation in human populations exposed to low levels of methylating carcinogens.

Length polymorphisms in human proline-rich protein genes generated by intragenic unequal crossing over

Southern blot hybridization analysis of genomic DNAs from 44 unrelated individuals revealed extensive insertion/deletion polymorphisms within the BstNI-type loci (PRB1, PRB2, PRB3 and PRB4) of the human proline-rich protein (PRP) multigene family. Ten length variants were cloned, including alleles at each of the four PRB loci, and in every case the region of length difference was localized to the tandemly repetitious third exon. DNA sequences covering the region of length variation were determined for seven of the alleles. The data indicate (1) that the PRB loci can be divided into two subtypes, PRB1 plus PRB2, and PRB3 plus PRB4, and (2) that the length differences result from different numbers of tandem repeats in the third exons. Variant chromosomes were also identified with different numbers of PRP loci resulting from homologous but unequal exchange between the PRB1 and PRB2 loci. The overall data are compatible with the observed length variants having been generated via homologous but unequal intragenic exchange. The results also indicate that these crossover events are sensitive to the amount of homology shared between the interacting DNA strands. Allelic length variants have arisen independently at least 20 times at the PRB loci, but only one has been detected at a PRH locus. Comparison of the detailed structures of the repetitious regions in PRB and PRH loci shows that the repeats in PRB genes are very similar to each other in sequence and in length. The PRH genes contain fewer repeats, which differ considerably in their individual lengths. These differences suggest that the larger number of length variants in PRB genes is related to their greater ease of homologous but unequal pairing compared to PRH genes.

Tubular site(s) of action of atrial natriuretic peptide in the rat

With micropuncture techniques, the present study examined the delivery of chloride to the superficial late distal tubule and the base and tip of the papillary collecting duct in rats treated with either Wy 47663, a synthetic analogue of atrial natriuretic peptide (ANP), or vehicle alone. Whole kidney glomerular filtration rate (GFR) and single-nephron glomerular filtration rate were not significantly different between the two groups. Late distal tubule chloride delivery was also not different between ANP- (5.71 +/- 1.15%) and vehicle- (6.28 +/- 1.12%) treated animals. However, fractional delivery to the base of the papillary collecting duct was significantly greater in the ANP-treated rats (14.37 +/- 1.98%) compared with vehicle-treated rats (7.32 +/- 1.47%). Tip papillary collecting duct delivery was also significantly greater in the ANP-treated rats (1.97 +/- 1.96 vs. 3.09 +/- 0.60%). In addition, the percent of chloride delivered that was reabsorbed along the papillary collecting duct was significantly less in the ANP-treated rats. In conclusion, ANP inhibits reabsorption in some tubular segments between the superficial late distal tubule and papillary collecting duct base as well as in the accessible portion of the papillary collecting duct.