PubMed Health⌕ Search

Biomedical subjects

K Kandarpa

Publications and source records attributed to K Kandarpa.

14 recordsLinked to original sources
PubMed1992

Endoluminal thermal occlusion of the ureter with the electromagnetic field-focusing device.

The authors attempted ureteral occlusion by means of heat application in nine ureters (24 sites) of New Zealand White rabbits with the electromagnetic field-focusing (EFF) device. The EFF device generates heat at the tip of a grounded probe by focusing eddy currents that have been induced within the tissues by an external radio-frequency field. The power settings were varied from 30 to 150 W. Heat was applied at multiple sites in each ureter. Immediate functional occlusion was seen in all nine ureters. Long-term complete occlusion was seen in six ureters at power settings ranging from 40 to 150 W, while long-term partial occlusion was seen in two ureters at 30-50 W. All sites at 30 W resulted in partial occlusions. Perforation of the ureter resulted in urinoma formation in one ureter at a site that was treated with 150 W. The EFF device can be used to endoluminally occlude the ureter by causing a fibrotic reaction to thermal injury. The effective power range for this application appears to be 40-100 W.

Animals↗
PubMed1992

Prospective double-blinded comparison of MR imaging and aortography in the preoperative evaluation of abdominal aortic aneurysms.

The authors conducted a prospective double-blind study comparing spin-echo axial and coronal magnetic resonance (MR) imaging with aortography in the preoperative evaluation of 20 patients with abdominal aortic aneurysms. Receiver-operating-characteristic (ROC) analysis was used to evaluate the performance of MR imaging versus aortography in assessing arterial stenotic disease. Both modalities were equivalent in demonstrating the upper extent of the abdominal aortic aneurysms with respect to the renal and visceral arteries. MR imaging was superior in demonstrating aneurysmal iliac arteries and intraluminal thrombus. Although aberrant venous anatomy, associated pathologic changes, and other concomitant lesions were demonstrated with MR imaging, it performed poorly in assessing arterial stenoses and occlusions. Thus, the authors caution against the routine substitution of spin-echo MR imaging for aortography in the evaluation of abdominal aortic aneurysms. Conventional angiography should continue to be performed in patients with suspected mesenteric ischemia, significant hypertension, and symptomatic iliofemoral atherosclerosis, at least until robust MR angiographic techniques have proved themselves under similar rigorous clinical evaluation.

Aged↗
PubMed1992

Quality assurance in cardiovascular and interventional radiology.

In summary, quality assurance in medicine and in CVIR must be an important part of daily practice. The JCAHO is gradually moving toward quality improvement as a goal, rather than simply monitoring performance. Physicians must lead the way in dealing with the issues of monitoring performance, with the ultimate goal being the welfare of their patients. The model SCVIR QA program described above will help cardiovascular and interventional radiology sections of all sizes to meet these goals. Resources applied toward QA activities are investments for maximizing efficiency and productivity, while minimizing morbidity and mortality. These well-spent efforts will hopefully decrease the spiraling costs of medical care.

Cardiovascular System↗
PubMed1991

Efficacy of thrombolysis in infrainguinal bypass grafts.

The initial outcome of a consecutive series of 43 intra-arterial urokinase infusions for thrombosed infrainguinal grafts in 37 patients was analyzed. There was an 88% (38/43) technical success rate (complete clot lysis) and a 74% (32/43) clinical success rate. Complications occurred in 10 patients (23%) and were related to bleeding in four patients (9%). Patient age, graft age, location, material, and the duration of occlusion did not significantly influence the initial outcome, although there was a trend toward a higher bleeding complication rate among grafts less than or equal to 1 month of age at the time of thrombolysis. A second group of 43 infrainguinal grafts successfully recanalized using regional infusions of thrombolytic agents were followed for long-term patency. This group included 32 grafts successfully treated with urokinase and 11 grafts recanalized with streptokinase. By life-table analysis there was a 55.6% 1-year patency, which fell to 42.4% at 4 years. Vein grafts had significantly (p = 0.01) better long-term patency than prosthetic grafts (69.3% versus 28.6% at 30 months). Grafts with flow-limiting lesions identified and corrected by angioplasty or surgery also had significantly (p = 0.01) better long-term patency than those without such lesions (79.0% versus 9.8% at 2 years). Based on the results of our study compared with a survey of long-term results following secondary surgical procedures for thrombosed infrainguinal grafts, thrombolysis can be recommended in several circumstances. Thrombolysis is indicated for thrombosed vein grafts or when thrombus is present in distal runoff vessels. Thrombosed prosthetic grafts should be replaced by autogenous vein grafts whenever possible.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1990

Recombinant tissue-type plasminogen activator versus urokinase in peripheral arterial and graft occlusions: a randomized trial.

A randomized prospective trial was undertaken to compare intraarterial administration of recombinant human tissue-type plasminogen activator (rt-PA) with urokinase (UK) in 32 patients with peripheral arterial or bypass graft occlusions. Sixteen patients were randomized to receive rt-PA and 16 to receive UK. The rt-PA dose was administered as a 10-mg bolus into the thrombus, followed by 5 mg/h for up to 24 hours. The UK dose was administered as a 60,000 IU bolus into the thrombus, followed by 240,000 IU/h for 2 hours, 120,000 IU/h for 2 hours, and 60,000 IU/h for up to 20 hours. Serial arteriograms were obtained at baseline and at 4, 8 or 16, and 24 hours. The endpoint was defined as 95% of greater clot lysis. The cumulative numbers of patients with successful thrombolysis (rt-PA vs UK) were four vs none at 4 hours, seven vs one at 8 hours, seven vs three at 16 hours, and eight vs six at 24 hours. Lysis occurred more rapidly in the rt-PA group (P = .04). Major bleeding complications occurred in five rt-PA patients and two UK patients (P = .39). At 24 hours, fibrinogen levels were significantly lower in the rt-PA group than in the UK group (P = .01). There was no apparent difference in 30-day clinical success.

Adult↗
PubMed1988

Forceful pulsatile local infusion of enzyme accelerates thrombolysis: in vivo evaluation of a new delivery system.

Forceful local pulsatile infusion of fibrinolytic enzyme disrupts thrombi, increases clot surface area, and thereby hastens enzyme action compared with conventional constant infusion methods, which are time consuming and therefore expensive. Prolonged thrombolytic therapy is associated with increased patient morbidity. A prototype for a clinically applicable pulsatile jet infusion system for accelerating thrombolysis was designed. The system is adaptable to standard angiographic catheters and techniques. The core of the system is a reciprocating syringe pump that delivers small volumes of thrombolytic enzyme in short, rapid, frequent pulses at high exit-jet velocity through any side-hole catheter (the smallest used was a 3-F catheter). Comparison of this system with a constant infusion system was made in vivo in a 48-hour-old thrombus model in rabbit inferior vena cava (IVC). One hour of lysis by streptokinase was conducted with each of the methods. In the first experiment, the IVC thrombi were left intact before chemical lysis. Pulsatile infusion lysed 61% of the thrombus by weight in an hour, whereas constant infusion lysed only 15% (P less than .001). In the second experiment, IVC thrombi were subjected initially to standardized mechanical perturbation by a guide wire before chemical lysis. In the latter experiment, pulsatile infusion lysed 54% of the thrombus by weight, and constant infusion lysed only 26% (P less than .005). The difference in percentage of lysis by weight between pulsatile infusion groups in the two experiments (61% vs 54%) was not significant (P greater than .1). The same was true of the difference between the two constant infusion groups (26% vs 15%, P greater than .05). The effect of initial perturbation of the thrombus by a guide wire appears to be less important than the thrombus disruption and accelerated thrombolysis caused by the pulsatile delivery system. No angiographic or macroscopically visible damage was seen in any IVC. Accelerated thrombolysis may reduce the expense, duration, and morbidity associated with conventional constant infusion methods.

Animals↗
PubMed1987

Quantification in peripheral angiography.

The purpose of this report is to review the wide variety of quantitative methods that either augment the angiogram or improve the evaluation of peripheral vascular disease when used in conjunction with the angiogram. The term "quantitative angiography" has many connotations in this area. On the one hand it may refer to any type of measurement of vessel diameter and luminal narrowing from angiographic images, or to an analysis of relative blood flow using videodensitometric methods. In the broader context it may mean any objective hemodynamic measurement that is obtained at the time of angiography, for example, pressure drop across a stenosis or blood flow studies using Doppler techniques. Lastly there are the indirect, noninvasive measurements that angiographers use, in conjunction with the patient history and clinical examination, to interpret the angiographic images. Doppler pressure measurements and plethysmography are two examples in wide clinical use. Magnetic resonance imaging (MRI) represents a noninvasive imaging modality that can concomitantly quantitate blood flow; however, its clinical utility in the evaluation of peripheral vascular disease is yet to be established.

Angiography↗
PubMed1987

Hemodynamic evaluation of arterial stenoses by computer simulation.

A new method to assess the hemodynamic severity of arterial stenoses was proposed and evaluated. It is based on a previously developed finite element computer simulation model for laminar-separated flow in arteries of axially varying cross-section; the present modification allows use of angiographic stenosis shapes acquired by automatic edge-detection algorithms. The method was validated by comparing its results with published experimental and theoretic results for ideal stenosis shapes. At moderate flowrates (Reynolds number = 500), poststenosis flow separation was predicted for moderately severe (75% area reduction) but not for mild (25%) stenoses. For high flowrates (Reynolds number = 900) in a severe stenosis (89%), stagnation and reversed flow were predicted and the experimental nondimensional pressure drop of 48.5 was correctly determined. Bernoulli's Equation, which neglects viscosity, predicted a drop of only 40. For a severe stenosis (89%), even at low Reynolds numbers (50), reversed flow agreeing with other theoretic solutions was predicted. Predictions are especially useful at low flow rates, where experiments are difficult to conduct. The height of the curve on the graph of nondimensional pressure gradient vs. Reynolds number reflects the hemodynamic severity of a particular stenosis; these curves were predicted for moderate and severe ideal stenoses and agree with experiments. A similar analysis is applied to an actual human coronary artery stenosis, and the results are demonstrated to have use in assessing interventions during angiography.

Arterial Occlusive Diseases↗
PubMed1986

Thrombolysis of occluded femoropopliteal grafts.

In a series of 44 occluded femoropopliteal grafts, streptokinase was used for thrombolytic therapy in 22 cases and urokinase in 22 cases. In most cases, thrombolytic agents were administered via an indwelling arterial catheter directly into the proximal thrombus. The catheter tip was advanced as thrombolysis occurred. Compared with streptokinase infusions, urokinase bolus injection followed by infusion had better results (77% vs 41%) and fewer complications (23% vs 50%). During thrombolytic infusion, concomitant heparin infusion was usually used to reduce the frequency of thrombus formation on the infusion catheter or recurrent thrombosis of the graft, once the tip of the infusion catheter was advanced distally. Follow-up in 23 of 26 successful cases showed that 11 of the grafts remained open at an average follow-up of 12 months or until the patient died. The 12 grafts that reoccluded remained open an average of 3 months. In none of the 18 failures was simple surgical thrombectomy or thrombectomy with graft revision effective in revascularizing the distal limb. The advantages of thrombolysis compared with thrombectomy are less trauma to the graft, which is especially important in vein grafts, and improved distal runoff due to lysis of infrapopliteal thrombus. Even among cases considered failures in this series, the surgical approach was often simplified because of partial thrombolysis. Thrombolysis requires a considerable amount of time, effort, and expense, but in certain patients where thrombectomy is indicated for the treatment of occluded femoropopliteal grafts this technique offers important advantages.

Aged↗