Alan P. Sawchuk

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.

Hypercoagulable states and lower limb ischemia in young adults

This study prospectively evaluates hypercoagulable states in patients under 51 years of age undergoing lower extremity revascularization for ischemia and assesses early outcome after operation. Twenty patients whose ages range from 23 to 50 years (mean 40.8 years) were identified prospectively who underwent lower extremity revascularization and evaluation of hypercoagulability. Fifteen patients were male (75%), 10 were black (50%), six had hypertension (30%), and four were diabetic (20%). All but two were cigarette smokers (90%). Seven aortoiliac procedures and 13 infrainguinal procedures were performed. Six patients had one or more abnormalities of regulatory proteins (protein S deficiency, four; protein C deficiency, three; presence of lupus-like anticoagulant, three; plasminogen deficiency, two). Eight of 17 patients in whom platelet aggregation profiles were obtained showed increased reactivity (47%). Only 4 of 17 patients (24%) were normal when tested for all parameters. Arterial or graft thrombosis developed in four of the 20 patients within 30 days after operation. Hypercoagulability was found in all four patients whose revascularizations failed. A high incidence of hypercoagulable states was found in patients under 51 years of age with lower limb ischemia requiring revascularization. Hypercoagulability may have contributed to early postoperative thrombosis of the vascular procedure.

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.

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.

Cerebral vascular reactivity assessed with acetazolamide single photon emission computer tomography scans before and after carotid endarterectomy

BACKGROUND AND METHODS In 64 patients, cerebral perfusion and vascular reactivity were assessed before and after carotid endarterectomy (CEA) using acetazolamide (ACZ)-enhanced single photon emission computer tomography (SPECT). Twenty-five patients were asymptomatic, whereas the remainder were symptomatic. Sixty-one patients had a > or = 70% ipsilateral internal carotid artery stenosis. RESULTS Fifty SPECT scans revealed decreased vascular reactivity. Twenty-three showed infarcts. Fourteen patients had normal studies. Twenty of the SPECT scans of asymptomatic patients demonstrated poor vascular reactivity. After CEA, 39 patients had improved ipsilateral vasoreactivity. In 12 patients, contralateral improvement was also found. CONCLUSION ACZ-enhanced SPECT scans, by assessing cerebral perfusion and vascular reactivity, may help to identify patients at risk of stroke should perfusion further diminish. Postoperative studies confirm improvement in vascular reactivity. ACZ-enhanced SPECT scans may provide objective evidence for the selection of patients with a high-grade asymptomatic carotid stenosis for CEA.

Aggressive management of vascular injuries of the thoracic outlet

PURPOSE We present a review of 35 patients who underwent an operation for subclavian (n = 18) or axillary (n = 17) vessel injury. In some patients, both an artery and a vein were damaged, resulting in a total of 30 arterial and 16 venous injuries. METHODS The wounding source included a gunshot (n = 19), a stab wound (n = 9,) and blunt trauma (n = 7). Seven patients had hypotension and were taken immediately to the operating room. Seventeen patients had diminished or absent pulses, whereas 13 patients had normal pulses despite an arterial injury. Associated injuries included nerve injury (n = 15), pneumohemothorax (n = 5), and fractures (n = 7). Angiography in 21 patients demonstrated an intimal flap (n = 8), extravasation (n = 5), a pseudoaneurysm (n = 3), an arteriovenous fistula (n = 2), and occlusion (n = 1). Two angiograms were normal. Arterial repair was accomplished by interposition graft (n = 17), primary repair (n = 9), patch angioplasty (n = 3,) and ligation (n = 1). RESULTS No functional deficits occurred in patients with an isolated vascular injury. Seven patients with associated brachial plexus injuries experienced severe disability. One arm of a patient was amputated. Two patients died. CONCLUSIONS The use of angiography helps to confirm and localize injuries. Prompt correction of the vascular injury avoids disability resulting from ischemia. Although the amputation rate is low with vascular repair, the functional disability resulting from associated nerve injuries can be devastating.

Carotid body tumors, inheritance, and a high incidence of associated cervical paragangliomas

BACKGROUND Current experience with carotid body tumors suggesting a high prevalence of associated cervical paragangliomas prompted this review. PATIENTS AND METHODS An 8-year retrospective study of patients with carotid body tumors was undertaken, detailing presentation, diagnosis, and treatment. RESULTS Eleven patients harboring 17 carotid body tumors were discovered. All patients had a neck mass. Seven patients (64%) had bilateral carotid body tumors. Six (55%) reported a positive family history-4 were first-generation relatives, 5 had bilateral tumors, and 3 had other head and neck paragangliomas. Angiography documented 4 associated vagal and 2 glomus jugulare paragangliomas in addition to the carotid body tumors. Precise surgical care limited blood loss to an average of 590 cc. The carotid artery was repaired during 5 resections (29%). Cranial nerve injury occurred in 3 cases, all following vagal body or glomus jugulare resection. Every patient is currently alive, stroke free, and functioning without major disability. CONCLUSIONS Patients with carotid body tumors have a propensity for multiple head and neck paragangliomas. Angiography is diagnostic. The need for associated paraganglioma resection dramatically increases the risk of cranial nerve injury.

Open transmetatarsal amputation in the treatment of severe foot infections

Severe forefoot infections may lead to limb loss, even if addressed aggressively. Infection or gangrene that compromises the plantar skin flap may preclude a standard transmetatarsal or midfoot amputation, thereby culminating in a below-knee amputation. We report a series of forefoot infections with loss of the distal plantar skin. Open or guillotine amputation at the mid-metatarsal level led to a high rate of healing and a durable stump, provided that the level of infection did not extend beyond the metatarsal heads. Wound closure was obtained by wound contracture alone or by use of partial-thickness skin grafting. Rehabilitation was dependable. The association of diabetes mellitus or gangrene did not adversely affect outcome. Open transmetatarsal amputation is a safe surgical option preferable to midfoot or below-knee amputation for the treatment of severe forefoot infection that does not extend proximally beyond the metatarsal heads.

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.

The fate of unrepaired minor technical defects detected by intraoperative ultrasonography during carotid endarterectomy

This report describes the natural history of unrepaired minor technical defects detected by intraoperative B-mode ultrasonography during carotid endarterectomy. Intraoperative ultrasonography was used to assess the technical adequacy of 80 carotid endarterectomies. Sixty-two arteries were normal on intraoperative ultrasound examination, whereas the remaining 18 arteries had a total of 21 minor residual technical defects. The 21 minor defects consisted of four internal carotid artery lesions, nine common carotid artery lesions, and eight external carotid artery lesions, 19 had 1 to 3 mm intimal flaps, and two had small stenoses. Sixteen of the 19 intimal flaps resolved before the first postoperative ultrasound study. These arteries had normal examination results, which indicated that these intimal flaps had healed. The two stenoses detected intraoperatively could not be detected by postoperative carotid duplex scanning at 1 month follow-up. No statistically significant relationship was found between the presence of a minor residual defect on intraoperative ultrasonography and the subsequent development of recurrent stenosis or occlusion in any of the arteries assessed. These data suggest that certain minor technical defects in the carotid artery that were detected by intraoperative ultrasonography are benign and may not require repeat exploration of the carotid artery for repair.