Robert S. Dieter

Lower extremity peripheral arterial disease in hospitalized patients with coronary artery disease.

The prevalence of coronary artery disease (CAD) in patients with peripheral arterial disease (PAD) has been well defined. However, the prevalence of PAD in hospitalized patients with CAD has not been defined. The ankle-brachial index (ABI) is a useful non-invasive tool to screen for PAD. The aim of our study was to assess the prevalence of PAD in hospitalized patients with CAD by measuring the ABI. The study was conducted at the University of Wisconsin Hospital and Clinics inpatient Cardiovascular Medicine Service. Medically stable patients with CAD were invited to participate prior to hospital discharge. Data regarding cardiovascular risk factors, history of previous PAD, physical examination, and ABI were collected. An ABI less than or equal to 0.9 or a history of previous lower extremity vascular invention was considered to be indicative of significant PAD. A total of 100 patients (66 men and 34 women) were recruited. Forty patients were found to have PAD (mean ABI in nonrevascularized patients with PAD = 0.67). By measuring the ABI, 37 (25 men) were positive for PAD and three had an ABI corrected with previous revascularization. Of these patients, 21 (52.5%) had previously documented PAD. Patients with PAD were older (p = 0.003), had a greater smoking history (p = 0.002), were more likely to have diabetes (p = 0.012), hypertension (p = 0.013) and a trend towards more dyslipidemia (p = 0.055). In conclusion, hospitalized patients with CAD are likely to have concomitant PAD. Risk factors for PAD in this patient population include advanced age, history of smoking, diabetes, hypertension, dyslipidemia and abnormal pulse examination. Identification of patients with PAD by measuring the ankle-brachial index is easily done.

Preliminary results of the initial United States experience with the Supera woven nitinol stent in the popliteal artery

BACKGROUND Popliteal artery stenting is not routinely performed due to concerns related to the high mobility of the knee joint and the potential for external stent compression, fractures, and occlusion. Open bypass is traditionally considered the gold standard for popliteal artery atherosclerotic lesions. The Supera stent (IDEV Technologies Inc, Webster, Tex) was developed to provide superior radial strength, fracture resistance, and flexibility compared with laser-cut nitinol stents. This study represents the initial United States experience in the management of popliteal artery atherosclerotic disease with the Supera interwoven wire stent. METHODS Patients undergoing stent implantation in the 20-month period after the 2008 Food and Drug Administration clearance were included. Medical records, radiographic imaging, and procedural data were examined. Procedural angiograms were classified according to Trans-Atlantic Inter-Society Consensus criteria. Patency and limb loss rates were calculated using Kaplan-Meier analysis. RESULTS A total of 39 stents were placed in 34 patients due to isolated popliteal artery occlusive disease. Clinical follow-up was a mean of 12.7 months (range, 0.2-33.7 months), and radiologic follow-up was a mean of 8.4 months (range, 0-26.8 months). Most patients had critical limb ischemia (CLI), with tissue loss (38.2%) or rest pain (35.3%) as the indication for intervention. In 20 patients (58.8%), the most distal end of the stent(s) landed in the below-the-knee popliteal segment, 12 (35.3%) landed in the above-the-knee segment, and two (5.9%) landed precisely at the knee. Other than angioplasty and stenting, 47% of patients did not receive any adjuvant concomitant therapy in the treated leg. Two patients underwent concomitant atherectomy of the popliteal segment. Primary, primary assisted, and secondary patency rates by duplex ultrasound imaging were 79.2%, 88.1% and 93%, respectively, by Kaplan-Meier estimates, with a mean stented length of 12 cm. Six instances of stent occlusion were noted, and six patients were identified with hemodynamically significant in-stent stenosis. Three patients sustained limb loss (8.8%), two related to uncontrolled infections, and one due to perioperative ischemic complications (both with patent stents at the time of limb loss). The overall mortality was 8.8% during the study period. Knee roentgenography was performed in all but one patient, and no stent fractures were identified. CONCLUSIONS Stenting of the popliteal artery using the Supera stent system appears to be safe and effective. The interwoven stent design may better serve areas under extreme mechanical stress. Our results with this highly diseased patient population justify a prospective trial in this subject.

Hypomagnesemia in Hemodialysis Patients: Role of Proton Pump Inhibitors

Background: Recent observations have associated hypomagnesemia with increased risk of cardiovascular morbidity and mortality in hemodialysis patients. Methods: We did a 3-month chart review of 62 chronic hemodialysis patients at a single US hospital. All were dialyzed using a dialysate [Mg] of 0.75-1.0 mEq/l. Patients were divided into two groups: hypomagnesemic (mean predialysis plasma [Mg] <1.5 mEq/l) and non-hypomagnesemic (mean predialysis plasma [Mg] ≥1.5 mEq/l). Results: All patients were male; mean age was 64.3 ± 8.7 years and the majority (73%) diabetic. 24 patients (39%) had hypomagnesemia and 38 (61%) were not hypomagnesemic. There were no significant differences between the two groups in age, diabetes status, blood pressure, duration of dialysis, plasma calcium, phosphorus, albumin, intact parathyroid hormone (PTH), dialysis adequacy (Kt/V), or dietary protein intake (as estimated by normalized protein catabolic rate, nPCR). However, use of proton pump inhibitors (PPIs) was significantly associated with hypomagnesemia (plasma [Mg] 1.48 ± 0.16 mEq/l in the PPI group vs. 1.65 ± 0.26 mEq/l in the non-PPI group, p = 0.007). Adjustment for age, diabetes status, duration of dialysis, plasma albumin, Kt/V, nPCR, and diuretic use did not affect the association between PPI use and hypomagnesemia. Conclusions: Use of PPIs in patients dialyzed using a dialysate [Mg] of 0.75-1.0 mEq/l is associated with hypomagnesemia. We suggest monitoring plasma [Mg] in patients taking PPIs, with discontinuation of the medication if possible and/or adjustment of dialysate [Mg] to normalize plasma [Mg].

Renal artery stenosis: epidemiology and treatment.

Renal artery stenosis (RAS) is a frequently encountered problem in clinical practice. The disease encompasses a broad spectrum of pathophysiologies and is associated with three major clinical syndromes: ischemic nephropathy, hypertension, and destabilizing cardiac syndromes. The two most common etiologies are fibromuscular dysplasia and atherosclerotic renal artery disease with atherosclerotic disease accounting for the vast majority of cases. Atherosclerotic renovascular disease has considerable overlap with atherosclerotic disease elsewhere and is associated with a poor prognosis. A wide range of diagnostic modalities and treatment approaches for RAS are available to clinicians, and with the advent of endovascular interventions, selecting the best course for a given patient has only grown more challenging. Several clinical trials have demonstrated some benefit with revascularization but not to the extent that many had hoped for or expected. Furthermore, much of the existing data is only marginally useful given significant flaws in study design and inherent bias. There remains a need for further identification of subgroups and appropriate indications in hopes of maximizing outcomes and avoiding unnecessary procedures in patients who would not benefit from treatment. In recent decades, the study of RAS has expanded and evolved rapidly. In this review, we will attempt to summarize the amassed body of literature with a focus on the epidemiology of RAS including prevalence, overlap with other atherosclerotic disease, and prognosis. We will also outline existing diagnostic and treatment approaches available to clinicians as well as summarize the findings of several major clinical trials. Finally, we will offer our perspective on future directions in the field.

Cell transplantation for treatment of left-ventricular dysfunction due to ischemic heart failure: from bench to bedside

Cell transplantation is an innovative technology that involves the implantation of a variety of myogenic and angiogenic cell types. The transplanted cells proliferate and augment left ventricular performance and therein ameliorate the heart failure symptoms. The concept of cell transplantation has followed the footsteps of angiogenesis starting as bench side research. The latter half of the decade saw the transformation of this potential mechanism to a promising therapy for ischemic heart failure. More than 150 patients have been treated with cellular transplantation worldwide. This novel application has the potential to revolultionalize alternative therapeutic approaches to management of heart failure.

Hypertrophy of Neurons Within Cardiac Ganglia in Human, Canine, and Rat Heart Failure: The Potential Role of Nerve Growth Factor

Background Autonomic imbalances including parasympathetic withdrawal and sympathetic overactivity are cardinal features of heart failure regardless of etiology; however, mechanisms underlying these imbalances remain unknown. Animal model studies of heart and visceral organ hypertrophy predict that nerve growth factor levels should be elevated in heart failure; whether this is so in human heart failure, though, remains unclear. We tested the hypotheses that neurons in cardiac ganglia are hypertrophied in human, canine, and rat heart failure and that nerve growth factor, which we hypothesize is elevated in the failing heart, contributes to this neuronal hypertrophy. Methods and Results Somal morphology of neurons from human (579.54±14.34 versus 327.45±9.17 μm2; P<0.01) and canine hearts (767.80±18.37 versus 650.23±9.84 μm2; P<0.01) failing secondary to ischemia and neurons from spontaneously hypertensive rat hearts (327.98±3.15 versus 271.29±2.79 μm2; P<0.01) failing secondary to hypertension reveal significant hypertrophy of neurons in cardiac ganglia compared with controls. Western blot analysis shows that nerve growth factor levels in the explanted, failing human heart are 250% greater than levels in healthy donor hearts. Neurons from cardiac ganglia cultured with nerve growth factor are significantly larger and have greater dendritic arborization than neurons in control cultures. Conclusions Hypertrophied neurons are significantly less excitable than smaller ones; thus, hypertrophy of vagal postganglionic neurons in cardiac ganglia would help to explain the parasympathetic withdrawal that accompanies heart failure. Furthermore, our observations suggest that nerve growth factor, which is elevated in the failing human heart, causes hypertrophy of neurons in cardiac ganglia.

Diagnostic Utility of Cardiac Troponin-I Levels in Patients with Suspected Pulmonary Embolism

Although positive troponin-I (TnI) assays have been reported in patients with pulmonary embolism (PE), Tnl levels in patients with suspected PE have not been evaluated systemati cally. The purpose of this study was to evaluate the diagnostic utility of Tnl measurements in patients with suspected PE. Consecutive patients with suspected PE were identified in whom nuclear ventilation/perfusion (V/Q) scans were performed and Tnl levels were measured. Tnl levels in patients with and without positive V/Q scans were compared by use of t tests. After categorizing Tnl levels as positive (Tnl-pos, ≥ 0.40 ng/mL) or negative, chi-square tests were used to relate these values to V/Q scan results. Separate comparisons were made for subjects with high-probability V/Q scans (V/Q-high, ≥90% likelihood of PE) and intermediate- or high- probability V/Q scans (V/Q-pos, ≥50% likelihood of PE). The mean Tnl level in the 10 subjects with V/Q-high scans was 0.39 ±0.79 ng/mL. The mean Tnl level in the 81 subjects without V/Q- high scans was 0.36 ±0.66 ng/mL (p = 0.89). Tnl levels did not differ between the 22 V/Q-pos subjects and the 69 subjects with negative V/Q scans (p = 0.86). A positive Tnl in the setting of V/Q-pos had a sensitivity of 32%, specificity of 71 %, positive predictive value of 26%, and a negative predictive value = 77% (chi-square = 0.06, p = 0.80). Elevated Tnl levels are not associated with positive V/Q scans. The Tnl assay is not a useful test in patients suspected of having PE, unless used to exclude myocardial ischemia or infarction.

Usefulness of Wide Pulse Pressure as a Predictor of Poor Outcome After Renal Artery Angioplasty and Stenting

Renal artery stenosis is a common cause of secondary hypertension and ischemic nephropathy. Percutaneous angioplasty and stent placement has allowed select patients with renal artery stenosis to use fewer antihypertensive agents and improve or stabilize renal function. The associations of baseline systolic, diastolic, and pulse pressures (PPs) with outcomes of blood pressure (BP) and renal function were examined in 243 patients who underwent renal angioplasty and stent placement. The average PP before the procedure in patients with improvements or stabilizations in renal function was 53 +/- 20 mm Hg, compared to 107 +/- 18 mm Hg (p <0.05) in those with poorer outcomes. The average PPs before procedure were 47 +/- 15 mm Hg in those with improvements in BP, 82 +/- 10 mm Hg in those with stabilizations of BP, and 111 +/- 14 mm Hg in those with worsening BP. All findings were statistically significant (p <0.05). In conclusion, wide PP may reflect more advanced vascular stiffness and renal disease distinguishing patients less likely to benefit from revascularization.

Invasive assessment of mitral regurgitation: Comparison of hemodynamic parameters

Objectives: We sought to analyze several new hemodynamic characteristics which address the interplay of left atrial (LA) and left ventricular (LV) pressures, as well as to re‐analyze several other V wave characteristics employed in the determination of mitral regurgitation (MR) severity in order to determine which, if any, had adequate correlation with grade of MR for clinical utility. Background: Invasive assessment of mitral regurgitation includes analysis of intracardiac pressures and LV angiography. The V wave, when obtained from the pulmonary capillary wedge position (PCWP), and its various characteristics are believed to be of limited value for prediction of MR severity. Method: We analyzed the transeptal pressure tracings of patients with various degrees of MR. Several relationships from the simuItaneous pressure‐time curves of the LA and LV were defined. Biplane left ventricular angiography was used to grade MR. Correlation between each parameter and MR grade was determined by calculating a Pearson correlation coefficient. Results: The ratio of the area under the V wave to the LV systolic area (Va/LVa) best correlates with the degree of MR with a Pearson correlation coefficient of 0.60. The Va/LVa was significantly lower in patients with 0−1+ MR compared to ≥2+ MR (0.14 vs. 0.23 p = 0.002). Conclusions: Invasive hemodynamic assessment of MR severity could be enhanced by calculating our new ratio, Va/LVa, due to its ability to account for LV work that is lost to the LA with a proportional decrease in forward or useful LV work with progressively increasing severity of MR.

Optimal use of left ventriculography at the time of cardiac catheterization: A consensus statement from the society for cardiovascular angiography and interventions

The rationale to perform left ventriculography at the time of cardiac catheterization has been little studied. The technique and frequency of use of left ventriculography vary by geographic regions, institutions, and individuals. Despite the recent publication of guidelines and appropriate use criteria for coronary angiography, revascularization, and noninvasive imaging, to date there have been no specific guidelines on the performance of left ventriculography. When left ventriculography is performed, proper technique must be used to generate high quality data which can direct patient management. The decision to perform left ventriculography in place of, or in addition to, other forms of ventricular assessment should be made taking into account the clinical context and the type of information each study provides. This paper attempts to show the role of left ventriculography at the time of coronary angiography or left heart catheterization. The recommendations in this document are not formal guidelines but are based on the consensus of this writing group. These recommendations should be tested through clinical research studies. Until such studies are performed, the writing group believes that adoption of these recommendations will lead to a more standardized application of ventriculography and improve the quality of care provided to cardiac patients.