Rajesh Subramanian

Renal fractional flow reserve: A hemodynamic evaluation of moderate renal artery stenoses

The objective of this study was to perform a hemodynamic evaluation of moderate (50–90%) renal artery stenosis (RAS) under conditions of rest and maximum hyperemia. Identifying patients with RAS who have hemodynamically significant stenoses and are most likely to benefit from revascularization is clinically important. Current methods used to evaluate RAS, including angiography, have limitations. Physiologic evaluation of RAS may have a role in identifying patients with hemodynamically significant stenosis. Patients with suspected renovascular hypertension due to aorto‐ostial RAS were included in the study. Hyperemia was induced by administration of intrarenal papavarine. Translesional pressure gradients were measured and renal fractional flow reserve (FFR) was calculated using a 0.014″ pressure guidewire. Thirteen patients and 14 arteries with moderately severe (50–90%) RAS were studied. The mean translesional pressure gradient rose from a baseline of 6.3 ± 3.9 to 17.5 ± 10.8 mm Hg with maximal hyperemia. The renal FFR ranged from 0.58 to 0.95. There was a poor correlation between angiographic stenosis measurement and the renal FFR (r = −0.18; P = 0.54) and the hyperemic translesional mean pressure gradient (r = 0.22; P = 0.44). There was an excellent correlation between renal FFR and the resting mean translesional pressure gradient (r = −0.76; P = 0.0016) and the hyperemic mean translesional pressure gradient (r = −0.94; P < 0.0001). Selective renal arterial papavarine administration induces maximum hyperemia, permitting the calculation of renal FFR in renal arteries with aorto‐ostial stenoses. The renal FFR correlates well with other hemodynamic parameters of lesion severity, but poorly with angiographic measures of lesion severity. Catheter Cardiovasc Interv 2005;64:480–486.

Predicting blood pressure improvement in hypertensive patients after renal artery stent placement: Renal fractional flow reserve

Background: Renal stent placement improves or cures hypertension in only 60–70% of patients with renal artery stenosis (RAS) and uncontrolled hypertension. There is a need to better identify patients who are likely to respond to percutaneous renal revascularization. We investigated whether an abnormal renal fractional flow reserve (FFR) would predict blood pressure improvement in patients undergoing renal artery stent placement. Methods: We prospectively enrolled 17 patients with unilateral RAS and medically refractory hypertension (BP > 140/90 mm Hg). Renal FFR was measured at maximal hyperemia induced by papaverine followed by renal stent placement. Blood pressure improvement was defined as a blood pressure of ≤140/90 mm Hg or an absolute decrease in diastolic blood pressure by 15 mm Hg on the same or less number of medications. Patients not meeting the above criteria were nonresponders. Results: Renal stent placement was successful in all patients. The average follow‐up was 10 ± 2 months. In patients with an abnormal renal FFR (< 0.80) blood pressure improved at 90 days in 86% compared with 30% in the normal renal FFR group (P = 0.04). Translesional pressure gradients (resting, peak, or hyperemic) alone failed to differentiate blood pressure responders from nonresponders. Conclusions: Renal FFR is a promising tool to identify patients likely to benefit following renal stent placement. This finding was independent of translesional pressure gradients, which did not predict blood pressure improvement. The ability to segregate patients with RAS and coexisting hypertension from those with renovascular hypertension may help clinicians select patients most likely to benefit from revascularization.

Nonhealing wound resulting from a foreign-body reaction to a radial arterial sheath

Several patients developed sterile inflammation at their radial arterial access site. Pathologic examination of biopsy material from one patient demonstrated a foreign‐body reaction to material most likely from the gel‐coated arterial access sheath. Surgical excision of the inflamed tissue resulted in healing. Cathet Cardiovasc Intervent 2003;59:205–206.

Catheter-Based Treatment for Patients With Acute Ischemic Stroke Ineligible for Intravenous Thrombolysis

Background and Purpose— We present our single-center experience using catheter-based therapy for acute ischemic stroke patients who were not candidates for intravenous thrombolytic therapy. Methods— Neurologic outcomes were assessed in patients with acute ischemic stroke, ineligible for intravenous thrombolysis, treated with an emergent catheter-based therapy. Results— Nonparametric analysis of neurological outcomes demonstrated a benefit in National Institutes of Health Stroke Scale (NIHSS) at long-term follow-up (P = 0.036). Independence in daily activities and improvement in NIHSS of ≥4 points were achieved in 38% and 56% of patients, respectively. Four patients (25%) died, including 2 patients (12.5%) who died from intracranial hemorrhage. Conclusions— Catheter-based treatment offers a promising treatment strategy in patients with acute ischemic stroke ineligible for intravenous thrombolysis.

Diabetes mellitus does not preclude stabilization or improvement of renal function after stent revascularization in patients with kidney insufficiency and renal artery stenosis.

Objective: To assess the impact of stent revascularization on the renal function of diabetic and nondiabetic patients with renal insufficiency. Background: Renal artery revascularization has been shown to stabilize or improve renal function in patients with significant renal artery stenosis and impaired renal function. However, some studies have suggested negligible or no benefit of renal function in diabetic patients with the same condition. Methods: We retrospectively compared data from 50 consecutive patients undergoing renal artery stent placement with renal insufficiency (serum creatinine ≥1.5–4.0 mg/dl) and global ischemia (bilateral or solitary [single] kidney renal artery stenosis) There were 17 diabetic (DM) and 33 nondiabetic (NDM) patients. The endpoints included the follow‐up measurements of renal function, blood pressure, and number of antihypertensive medications. Results: After stent placement, at a mean follow‐up of 42 ± 18 months (range: 6–62 months), 79% NDM (N = 26), and 76% DM patients (N = 13) (P = NS) had improvement in the slope of the reciprocal of creatinine (1/SCr), indicating a beneficial effect in renal function in many patients. Conclusion: Renal artery stent placement appears to be equally beneficial in preserving renal function in DM and NDM patients with ischemic nephropathy and global renal ischemia.