Biomedical subjects

M C Dalsing

Publications and source records attributed to M C Dalsing.

At least 37 records · Page 2Linked to original sources

PubMed1996

Wall remodeling during luminal expansion of mesenteric arterial collaterals in the rat.

Wall remodeling associated with rapid luminal enlargement of collateral mesenteric arteries in rats was investigated 1 and 4 weeks after creation of a collateral pathway by ligating three to four sequential arteries. Paired observations were made of inner diameters of collateral and normal arteries in the same animals. Arterial blood flow was measured at the final observation. Sections of arteries were processed for morphological measurements. After 4 weeks, inner arterial diameter was increased more at the beginning (63 +/- 6%) than the end (25 +/- 9%) of the collateral pathway. At 1 and 4 weeks, respectively, cross-sectional areas of collateral relative to normal arteries were increased by 46 +/- 5% and 59 +/- 13% (lumen), 55 +/- 8% and 65 +/- 14% (media), and 89 +/- 18% and 60 +/- 31% (intima). The wall expansion during luminal enlargement resulted in a normal medial thickness:luminal radius relationship. At 1 week postligation, wall shear rate remained elevated and endothelial but not smooth muscle hyperplasia had occurred (intimal nuclei: 40 +/- 1.7 collateral versus 24 +/- 3.0 normal; medial nuclei: 42 +/- 6.8 collateral versus 37 +/- 2.1 normal). At 4 weeks, wall shear rate in collaterals was similar to normal arteries, and smooth muscle hyperplasia had taken place (medial nuclei: 84 +/- 9.4 collateral versus 44 +/- 4.7 normal). The data demonstrate that wall expansion associated with rapid luminal enlargement of these collaterals involves hyperplasia of both endothelial and smooth muscle cells; however, smooth muscle proliferation does not occur until after wall shear rate is reduced. The specific cellular adaptations that occur during collateral development may depend on the level of wall shear and shear-dependent modulation of endothelial growth factors.

Animals↗

PubMed1995

A comparison of endovascular assisted and conventional in situ bypass grafts.

Thirty-three in situ saphenous vein bypass grafts were performed using a conventional open technique (CI) while 31 in situ bypass grafts were performed using endovascular occlusion of side branches (EAI). Bypass grafts were performed from the femoral to the popliteal (n = 37) or a trifurcation (n = 27) artery for claudication (n = 7), rest pain (n = 14), or tissue loss (n = 43). Wound complications developed in 11 Cl and four EAI limbs. Postoperative hospitalization in CI and EAI patients was, respectively, 8.4 +/- 2.0 days and 4 +/- 1.6 days. Missed arteriovenous fistulas were noted in one CI and 17 EAI limbs postoperatively. At follow-up four (12%) CI and six (19%) EAI grafts were occluded or had undergone revision surgery. Based on life-table analysis CI and EAI cumulative patency rates at 18 months were 79% and 83%, respectively. Although this new technique (EAI bypass grafting) did not reduce operative time, it did decrease the length of surgical incisions and the duration of postoperative hospitalization (p < 0.001, Student's t test). Wound complications occurred less frequently in EAI limbs but the incidence of missed arteriovenous fistulas was significantly higher. These data suggest that EAI and CI patency is comparable. Ultimately long-term patency will be the crucial test for determining the utility of this new technique.

Adult↗

PubMed1995

Long-term follow-up of the Palmaz stent for iliac occlusive disease.

BACKGROUND: Thirty-eight limbs with iliac occlusive disease were treated with Palmaz stents from 1987 through 1991. METHODS: Indications for stent utilization included dissection induced by percutaneous transluminal balloon angioplasty (PTA) (10), restenosis after PTA (nine), post-PTA residual stenosis (nine), multiple stenoses or occlusion (five), and unfavorable location (five). RESULTS: The ankle/brachial pressure index increased from 0.53 +/- 0.27 to 0.8 +/- 0.26 after stent deployment. The intraluminal pressure gradient decreased from 31.9 +/- 16.3 to 0.9 +/- 2.2 mm Hg after stent deployment. Complications included pseudoaneurysm (one), arteriovenous fistula (one), iliac perforation (one), groin hematoma (two), and occlusion (two). Follow-up arteriogram showed stenosis proximal or distal (n = 4) or within the stents (n = 4). These were treated with PTA or stents. Two patients required an aortobifemoral graft. Nine patients have died. Life table analysis showed a 1-, 3-, and 5-year primary and secondary cumulative patency of 87% +/- 5.9%, 74% +/- 8.2%, and 63% +/- 10% and 91% +/- 5.1%, 91% +/- 5.6%, and 86% +/- 7.6%, respectively. CONCLUSIONS: Palmaz stents, often required to salvage a PTA failure, appear to maintain overall patency at a high level. However, intimal hyperplasia and the progression of atherosclerotic disease may result in a need for additional procedures to obtain this favorable outcome.

Adult↗

PubMed1995

Femorodistal vein grafts: the utility of graft surveillance criteria.

PURPOSE: This retrospective review of femorodistal vein grafts was analyzed to determine the usefulness of various graft surveillance criteria. METHOD: The surveillance schedule involved evaluations at 1 month, every 3 months the first year, and then every 6 months. Salvage intervention or graft occlusion occurring within the next follow-up interval defined surveillance end points. One hundred two grafts (329 surveillance visits) had an ankle/brachial index (ABI). A duplex scanning-determined midgraft peak systolic flow velocity (PSFV) was available for 81 grafts (262 visits). Forty-eight grafts (137 visits) had both a PSFV and entire graft duplex scanning (EGDS) to determine stenosis greater than 50%, whereas 40 grafts (91 visits) had simultaneous ABI and EGDS. RESULTS: When a greater than 15% decrease in ABI denoted an abnormal surveillance study result, a positive predictive value (PPV) of 24.3% and negative predictive value of 94.5% were noted. Similarly, a PSFV cutoff of less than 35 cm/sec demonstrated values of 26.3% and 94.2%, respectively. When an EGDS of greater than 50% stenosis or a PSFV of less than 35 cm/sec were the cutoff criteria, the PPV was 36.7% and negative predictive value 99.1%, whereas characterizing abnormal results further with ABI (> 15% decreases) increased the PPV to 83.3%. CONCLUSION: The combination of an EGDS, midgraft PSFV, and ABI provides optimal follow-up for our patients with a femorodistal vein graft.

Ankle↗

PubMed1995

Iliac artery MR angiography: comparison of three-dimensional gadolinium-enhanced and two-dimensional time-of-flight techniques.

PURPOSE: To determine if a three-dimensional (3D) gadolinium-enhanced technique is useful for improving the accuracy of magnetic resonance (MR) angiography. MATERIALS AND METHODS: Prospectively, two-dimensional (2D) time-of-flight (TOF) and 3D gadolinium-enhanced MR angiography was performed in 23 patients. Conventional arteriography, the reference standard, was performed in all but five patients. Images from each examination were interpreted blindly by two observers. RESULTS: For common and external iliac arteries, interpretations of dynamic 3D gadolinium-enhanced MR angiograms matched those of conventional arteriograms in 12 of 18 patients (67%) for both observers. Interpretations of 2D TOF images matched those of conventional arteriograms in six (33%) and seven (39%) patients for the two observers respectively. CONCLUSION: Preliminary results suggest that iliac artery MR angiography can be improved by complementing standard 2D TOF acquisitions with 3D gadolinium-enhanced acquisitions.

Angiography↗

PubMed1994

Early results of endovascular-assisted in situ saphenous vein bypass grafting.

PURPOSE: This study evaluated an endovascular technique for occlusion of arteriovenous fistula when performing saphenous vein in situ bypass grafting. METHODS: In 31 limbs femoropopliteal (17) or femorotibial (14) in situ bypass grafting was performed for claudication/aneurysm (4), rest pain (6), or tissue loss (21). A valvulotome was used for valve lysis. Saphenous vein branches were identified with angioscopy in 16 limbs or with fluoroscopy in the remainder. An electronically steerable endovascular catheter was used to deliver platinum coils into the venous tributaries to occlude them. RESULTS: The maximal number of coils placed in any limb was nine. Most operations were performed with only a groin incision (length = 9.8 +/- 1.6 cm) and a distal incision (length = 16.8 +/- 6.5 cm). Wound complications occurred in four limbs, whereas four limbs developed localized superficial thrombophlebitis. The postoperative ankle-brachial index increased to a mean of 0.91 +/- 0.12. Postoperative duplex imaging revealed a missed arteriovenous fistula in 12 limbs. Two were surgically ligated, whereas the remainder were embolized in the radiology suite. Postoperative length of hospitalization was 4 +/- 2 days in uncomplicated cases. Follow-up revealed five graft occlusions. Occlusion occurred at 12 hours, 2 weeks, and 6, 14, and 15 months after operation. Although there were no perioperative deaths, two patients have died of unrelated causes. CONCLUSION: This endovascular technique of arteriovenous fistula embolization decreased the length of the surgical wounds, and patients were discharged 4 +/- 2 days in uncomplicated cases. The ultimate test of its efficacy, however, will be long-term functional results.

Adult↗

PubMed1994

A prospective, in vivo study of the relationship between blood flow hemodynamics and atherosclerosis in a hyperlipidemic swine model.

PURPOSE: This is the first prospective evaluation of the relationship between shear stress and atherosclerotic plaque formation in a pulsatile, in vivo model. METHODS: A 50% aortic stenosis was created in six Yucatan micropigs by placing a suture line across the left half of the aorta. A specially modified 20 MHz Doppler ultrasound probe mounted at a 45 degree angle on a micromanipulator was used to measure blood flow velocity along the lateral aspects of the aorta. Shear stress at these locations was calculated with linear regression. The pigs were then fed a specially formulated hyperlipidemic diet for 7 months, after which their aortas were harvested. Plaque thickness was measured and correlated with mean, maximum, and minimum shear stress at each site and side on or away from the aortic plication and distance from the level of the aortic plication with general linear modeling. RESULTS: Plaque thickness was negatively correlated with the mean shear stress during the cardiac cycle (correlation coefficient -0.3972 p = 0.0164) and with the maximum shear stress during the cardiac cycle (correlation coefficient -0.4581 p = 0.0050). Plaque thickness was correlated with a multivariate model of mean shear stress, maximum shear stress, and their interactive effects with other parameters in the model with a correlation coefficient of 0.6733, (p = 0.0048). CONCLUSIONS: This is the first prospective, in vivo study with a pulsatile, hyperlipidemic model, which clearly demonstrates that low shear stress is associated with plaque formation.

Animals↗

PubMed1994

Valve transplantation to the canine popliteal vein: the utility of a distal arteriovenous fistula and the hemodynamic result of a single functional valve.

PURPOSE: The objectives were to transplant a venous valve into the popliteal vein of a canine insufficiency model that would maintain long-term function and then to measure the hemodynamic benefit of such a valve. METHODS: Indexes of venous valvular function, including venous filling time, 90% of venous refilling time, and simulated ambulatory venous pressure, were measured in 11 greyhounds before intervention (Control) and after hind limb venous valvulotomy, which produces chronic venous insufficiency. Three weeks later a valve-containing segment of external jugular vein was transplanted to the popliteal vein with (n = 6) or without (n = 5) a distal arteriovenous fistula. The fistula was ligated in 4 to 6 weeks. Repeat venous indexes were obtained an average of 2 weeks after the last operative intervention. Gross anatomic inspection +/- duplex scanning performed before the animals were killed were used to distinguished normal from damaged valves. RESULTS: Four of five simple valve transplants demonstrated scarring and/or thrombosis and the average venous filling time, ambulatory venous pressure, and 90% of venous refilling time were consistent with chronic venous insufficiency and/or obstruction. One fistula failed in the six valve distal arteriovenous fistula transplants, and that valve was incompetent. Analysis of the remaining five functional valves demonstrated venous filling time consistent with chronic venous insufficiency, normalization of ambulatory venous pressure, and 90% of venous refilling time between normal, and chronic venous insufficiency. These valves appeared normal. CONCLUSIONS: Popliteal vein valve transplant anatomy is preserved by an adjunctive distal arteriovenous fistula, and a competent valve transplant improves postexercise venous hemodynamics to approach those of a normal limb.

Analysis of Variance↗

PubMed1994

Acute compensation to abrupt occlusion of rat femoral artery is prevented by NO synthase inhibitors.

The hemodynamic significance of endothelium-derived relaxing factor (EDRF)-mediated mechanisms in vascular responses to abrupt rat femoral artery occlusion was investigated. Temporary arterial occlusion was produced before and after inhibition of nitric oxide synthase by N omega-nitro-L-arginine methyl ester (L-NAME) or NG-monomethyl-L-arginine (L-NMMA). Iliac artery blood flow and arterial pressures proximal and distal to the occlusion were measured. Normal vascular compensation included a return of resistance to preocclusion levels and a rise in distal pressure to a plateau within 5 min postocclusion. After treatment with L-NAME and L-NMMA, postocclusion resistance remained elevated by 53 and 36%, respectively. Collateral dilation after occlusion, as indicated by the rise in distal pressure, was prevented by L-NAME but not L-NMMA. Increases in adrenergic tone and mean arterial pressure by phenylephrine did not prevent compensation, suggesting the effects of L-NAME and L-NMMA did not result from elevated sympathetic activation or pressure. The results are consistent with the hypothesis that the stimulated release of endothelium-derived relaxing factor mediates the acute vascular compensation to abrupt arterial occlusion.

Amino Acid Oxidoreductases↗

PubMed1993

Preliminary experience with transluminal laser-induced intrahepatic portacaval shunts.

This study investigated the feasibility of performing an intrahepatic portacaval shunt (IHPCS) by means of transluminal laser angioplasty. In 10 anesthized dogs, a catheter was introduced into a mesenteric vein and threaded into the portal vein (PV). Under fluoroscopy, a Ross needle was passed through the PV catheter, liver, and into the intrahepatic IVC. Following guidewire exchange, a neodymium YAG laser hot-tip probe (power setting 8 W) was passed over the guidewire to accomplish a transluminal IHPCS. In five animals, an IHPCS could not be accomplished. Initial and subsequent patency was confirmed by fluoroscopy. These early data suggest that transvenous laser-induced intrahepatic portacaval shunts may be feasible as a means of decompressing portal hypertension. Further research is necessary, to investigate the long-term patency as well as this technique's ability to decompress the portal system.

Aluminum Silicates↗

PubMed1993

Vascular surgery-associated ureteral injury: zebras do exist.

This report describes a case of direct ureteral injury sustained during retroperitoneal vascular surgery. The diagnosis was delayed and treatment was complicated by infection. To address the patient's problem initially and then to consolidate our impressions, a literature review was undertaken. The conclusions from this review suggest that direct ureteral injury during vascular surgery is rare but most common during redo surgery, is just as likely to be missed as discovered during surgery, and when missed may be so for months. The diagnostic delay is caused by a varied and often misleading presentation, and a ureteral contrast study is the ultimate diagnostic tool. In these delayed cases the typical ureteral treatment is a stented ureteroureterostomy or nephrectomy. In the present case the patient was otherwise healthy; therefore an aggressive attitude to renal salvage was taken. This is a unique case of ileal conduit replacement of the damaged ureter for this specific situation. Five years after repair, renal function is stable without infectious complications. The current literature would suggest that the vascular graft may be left undisturbed if the urine is sterile. If infection is present, graft removal appears the standard of care and was successful in the present case.

Aorta, Abdominal↗

PubMed1993

Allastair B. Karmody Award. Improved recovery of limb function with ATP/MgCl2 in an ischemic canine hind limb.

The ability of a solution of low-vanadium-content (less than 1 ppm) adenosine triphosphate and magnesium chloride (ATP/MgCl2) versus normal saline to improve recovery of function and reduce necrosis of skeletal muscle after severe ischemia was investigated in an in situ autoperfused canine hind limb model. The study consisted of 12 dogs divided into 3 study groups: nonischemic control (NIL) (n = 7 limbs), ischemic (IL) (n = 7 limbs), and ischemic ATP/MgCl2-treated (IATP) (n = 7 limbs). In groups IL and IATP, the limb was reperfused for 3 hours following 4 hours of complete ischemia. In IATP limbs, 200 mumol/kg of ATP/MgCl2 was infused upon reperfusion of the limbs, whereas IL limbs received a similar volume of normal saline at the time of reperfusion. Function was determined by stimulating the deep peroneal nerve and anterior tibial muscle and measuring the resultant isometric twitch contractile force of paw dorsiflexion. Muscle necrosis was evaluated by photographic analysis of sectioned anterior tibial muscle stained with nitroblue tetrazolium dye. ATP/MgCl2 significantly increased functional recovery (p < 0.01) and significantly reduced skeletal muscle necrosis (p < 0.01). This study suggests that ATP/MgCl2 may be useful in reducing the clinical sequelae of severe limb ischemia and reperfusion.

Adenosine Triphosphate↗

PubMed1993

Vascular injuries during pancreatobiliary surgery.

Fourteen cases of vascular injury during pancreatobiliary surgery have been treated at our institution. The patients' mean age was 49 years, and nine were males. Six operations were performed for chronic pancreatitis, six for cancer, and two for an inflammatory process. Operations included 11 pancreatic resections and one laparoscopic cholecystectomy, one sphincteroplasty, and one pseudocyst drainage. Vessels injured included the portal vein (7), superior mesenteric vein (6), superior mesenteric artery (3), hepatic arteries (4), splenic vein (3). Six patients experienced more than one vascular injury. In all but one case, the injury was recognized and repaired during the initial operation. Primary repair was possible in seven cases. Six cases utilized autogenous tissue for repair. The one unrecognized injury was a right hepatic artery ligation, and a delayed repair was not possible. Follow-up demonstrated two occlusions, one following a portal vein repair without clinical sequela and a superior mesenteric artery repair which resulted in a small bowel stricture. The one unrecognized hepatic artery injury resulted in necrosis of the proximal common hepatic duct. Vascular injury following pancreatobiliary injury tends to occur in the presence of pancreatitis or cancer with its associated dense adhesions and inflammatory process. The variable anatomy of this area contributes to vascular injuries. Immediate recognition of the injury and repair appears to yield excellent results.

Adolescent↗

PubMed1992

Laser and suture anastomosis: passive compliance and active force production.

One carotid from each dog underwent a laser anastomosis and the other carotid an interrupted suture repair. One or eight weeks later (n greater than or equal to 4 dogs/time period); four rings (1 mm in length) containing the laser or suture anastomosis or the normal artery (two/dog) were removed. Using a photoelectric force transducer and lever system, the ring was stretched in increments and passive force measured. At each length, the arterial muscle was stimulated and active force measured. The mean laser and control passive length/tension (L/T) curves were not different (P greater than 0.05), but the suture curve was shifted downward (P less than 0.05). The mean laser and suture active L/T curves were similar at 1 week (greater than 0.05) and lower than the control curve (P less than 0.04). At 8 weeks, the laser-repaired vessels produced an active force similar to control muscle (P greater than 0.05) but the suture repairs could not generate this active force (P less than 0.05). These data suggest that the laser repair and normal artery are more mechanically compatible than the suture repair as studied by this method.

Anastomosis, Surgical↗

PubMed1992

Initial results of endothelial cell seeding following argon laser carotid endarterectomy.

This study evaluates the initial results of endothelial cell (EC) seeding following argon laser carotid endarterectomy. Venous endothelial cells were harvested from 12 dogs and cultured. A laser endarterectomy was performed on both carotids of each dog. One side was seeded with endothelial cells. Six dogs had both carotids harvested 1 hour after restoring blood flow. The others were harvested in 24 hours. The percentage of lumen covered with EC was evaluated by scanning electron microscopy. At 1 hour, the seeded arteries demonstrated 35 +/- 3 percent EC coverage, whereas the unseeded arteries had no EC coverage (P = 0.0002). At 24 hours, the seeded arteries had 58 +/- 15 percent EC coverage, whereas the unseeded arteries had no coverage (P = 0.01). Significant gross thrombus developed only in unseeded arteries (P = 0.047), two of which were occluded at 24 hours. EC seeding is beneficial following argon laser carotid endarterectomy resulting in improved patency and less surface thrombogenicity.

Animals↗

PubMed1992

Dobutamine stress echocardiography as a predictor of cardiac events associated with aortic surgery.

Two-dimensional echocardiography can detect regional wall motion abnormalities resulting from myocardial ischemia produced by dobutamine infusion. In 60 patients undergoing elective aortic surgery (27 with aneurysms, 33 with occlusive disease), we evaluated the ability of dobutamine stress echocardiography to predict perioperative cardiac events. Echo images were obtained at rest and during incremental dobutamine infusion to a peak dose of 50 micrograms/kg/min, unless another test end point was reached (angina, heart rate greater than or equal to 85% of age-predicted maximum, significant ST segment depression, or new stress-induced wall motion abnormalities). Dobutamine stress echocardiography results were stratified as follows: group I, no wall motion abnormalities; group II, resting wall motion abnormalities unchanged with stress; group III, stress-induced worsening of resting wall motion abnormalities; group IV, new-onset wall motion abnormalities with stress. Twelve cardiac events occurred within the first 30 postoperative days: three cardiac deaths (5%), six nonfatal myocardial infarctions (10%), two patients with unstable angina (3.3%), and one patient with asymptomatic elevation of creatine phosphokinase MB isoenzymes without electrocardiographic changes (1.7%). Eleven events occurred in the 38 patients with an abnormal dobutamine stress echocardiograph (groups II to IV); in contrast, only one of 22 patients with a normal dobutamine stress echocardiograph (group I) had a cardiac event. These event rates (29% vs 4.6%) differed significantly (p less than 0.025). Dobutamine stress echocardiography is a new, safe, rapid, relatively low cost, noninvasive, nonexercise cardiac stress test for risk stratification before major vascular surgery.

Aged↗

PubMed1992

Acetazolamide enhanced single photon emission computed tomography (SPECT) evaluation of cerebral perfusion before and after carotid endarterectomy.

Twenty-five patients were tested before and after carotid endarterectomy with resting and acetazolamide enhanced single photon emission computed tomography (SPECT) scans with hexamethyl propyleneamine oxine (HMPAO) or iofetamine hydrochloride I123 (123I labeled IMP), both widely available radiopharmaceuticals. Twenty preoperative SPECT studies were asymmetric, revealing focal or diffuse decreased perfusion reserve, and 13 also demonstrated infarcts. Five patients had symmetric (normal) studies. After carotid endarterectomy, 22 cases had changed flow distribution patterns. Usually improvement of reactivity ipsilateral occurred to the area operated on. In four, contralateral improvement was also found. Three of the patients who had preoperative symmetrical scans had increased ipsilateral reactivity after surgery indicating previous global loss of reactivity. Acetazolamide SPECT scans demonstrate a decreased perfusion reserve in 20 patients with carotid artery stenosis, indicating reduced perfusion and poor collateral circulation. Postoperative studies confirm improvement by demonstrating recovery of vascular reactivity in 84% of the patients. Acetazolamide enhanced SPECT scans may be helpful in providing objective evidence for selection of patients for carotid endarterectomy, especially in those who have an 80% carotid artery stenosis, but are asymptomatic.

Acetazolamide↗

PubMed1991

Early experience with the Palmaz expandable intraluminal stent in iliac artery stenosis.

Since 1987, we have used the Palmaz expandable intraluminal stent in 22 selected cases of iliac artery stenosis in 14 men and six women with a mean age of 63 years for claudication (9), graft salvage (5), rest pain (4), and tissue loss (2). Morphologic criteria included severe percutaneous balloon angioplasty-induced dissection (6), long or multiple stenoses or occlusions (5), post-percutaneous balloon angioplasty elastic recoil (4), location of stenosis (4), and restenosis following percutaneous balloon angioplasty (3). Twenty-two limbs were treated with 61 stents. The mean pressure gradient across the lesion fell from 31 +/- 15 to 1.1 +/- 2.4 mmHg after stenting. The mean ankle/brachial systolic pressure index improved from 0.59 +/- 0.31 to 0.83 +/- 0.25 after stenting. The mean follow-up is 11.4 months, with a mean ankle/brachial index at their most recent follow-up of 0.88 +/- 0.19. Symptomatically, 11 extremities are normal and five limbs are improved. Three patients have died and two have required bypass grafts for iliac occlusive disease. In this early experience, the Palmaz intraluminal stent appears to be valuable for the management of post-percutaneous balloon angioplasty restenosis, elastic recoil, and percutaneous balloon angioplasty-induced dissection, although it is not without complications.

Angioplasty, Balloon↗