Myocardial infarction determined by technetium-99m pyrophosphate single-photon tomography complicating elective coronary artery bypass grafting for angina pectoris.

The incidence of acute myocardial infarction (AMI) complicating coronary artery bypass grafting (CABG) has previously been based on concordance of electrocardiographic, enzymatic and scintigraphic criteria. Technetium-99m pyrophosphate (Tc-PPi) single-photon emission computed tomography now enables detection of AMI with high sensitivity and specificity. Using this technique, perioperative AMI was detected in 12 of 58 patients (21%) undergoing successful elective CABG for stable angina pectoris. Stepwise multivariate logistic regression analysis was performed to compare the predictive value of preoperative (New York Heart Association class, left ventricular ejection fraction and use of beta blockers) and intraoperative (number of grafts constructed, use of internal mammary anastomoses, use of sequential saphenous vein grafts, smallest grafted distal vessel lumen caliber and aortic cross-clamp time) variables. Preoperative New York Association class (p = 0.04) and smallest grafted distal vessel lumen caliber (p = 0.03) were significant multivariate predictors of perioperative AMI. Only 1 perioperative patient with AMI (and 1 pyrophosphate-negative patient) developed new Q waves. Serum creatine kinase-MB was higher in patients with AMI by repeated measures analysis of variance (p = 0.0003). Five AMIs occurred in myocardial segments revascularized using sequential saphenous vein grafts, and 7 in segments perfused by significantly stenosed epicardial vessels with distal lumen diameter and perfusion territory considered too small to warrant CABG. At 6-month follow-up, the mean left ventricular ejection fraction increased from 0.61 to 0.65 in Tc-PPI-negative patients (p = 0.01), but not in perioperative patients with AMI.(ABSTRACT TRUNCATED AT 250 WORDS)

Simultaneous aortic and renal artery reconstruction for acute arterial occlusion in solitary kidney.

A case is described of the onset of acute renal failure due to renal artery occlusion in a solitary kidney of a sixty-six-year-old woman. She had been treated for severe hypertension due to renal artery stenosis. An aortorenal bypass to revascularized the kidney was combined with repair of an abdominal aortic aneurysm. There was early and full recovery of renal function in the single kidney, and the patient was completely rehabilitated. Review of the literature shows that an aggressive surgical approach to the management of renal artery occlusion is usually followed by excellent results. The pre-existence of renal artery stenosis encourages the formation of a collateral arterial supply which maintains the nutrition of the kidney almost indefinitely, after renal artery occlusion. Revascularization will result in prompt recovery of renal function.

Radiation damage to large arteries.

Little is known about late changes in large arteries after radiotherapy. Much more is known about damage to other organs and tissues. The arterial changes resemble chronic, progressive atherosclerosis which may be due to a combination of periarterial fibrosis, direct damage to the arterial wall, occlusion of vasa vasorum and acceleration of naturally occurring atherosclerosis. Factors that may predispose to arterial occlusion that relate to radiotherapy include maximum tissue dose, beam energy and field size. The authors present four patients with axillary artery occlusion that occurred 10 to 27 years after mastectomy and irradiation. The axillary artery is seldom affected by segmental atherosclerotic occlusive disease. Hence, the cause of the occlusion was most likely the irradiation. All patients did well after bypass grafting.

Acute and chronic clinical performance comparison of a porous and a solid electrode design.

The long-term performance of porous and solid ring-tipped electrodes was compared in clinical use over a one-year period. Each of the two electrode designs was implanted in 22 patients in conjunction with an output-programmable pacemaker. Implant evaluation included impedance, height of sensed R wave, and a strength-duration curve. Threshold determination by pulse-width programming was performed at the time of implant and at one week, two weeks, two months, six months, and one year. There were no dislodgements with either electrode. No significant differences were noted in the acute parameters or in chronic thresholds.

Prevention of severe intestinal ischemia following reconstruction of the abdominal aorta.

Intestinal ischemia should be suspected in any patient following aortic surgery who has pain out of keeping with the operation, postoperative diarrhea (with or without bleeding) or an unexplained metabolic acidosis. Ten such cases of intestinal ischemia were identified during a 10-year period at the Toronto General and Toronto Western hospitals. Six occurred following repair of a ruptured abdominal aneurysm, one followed elective aneurysmectomy and three followed elective bypass for occlusive disease. The overall mortality was 70%. Transmural bowel infarction was found in six patients (all died), while four patients had partial-thickness injury (one died, three had late strictures). Potentially preventable factors in each patient, either single or multiple, were identified and are discussed. Emphasis on ealy diagnosis is stressed, because once transmural necrosis had occurred the prognosis is poor.

Comparison of conduits for leg revascularization.

The saphenous vein (SV) remains the conduit of choice for lower limb revascularization. When SV is unavailable, or unsuitable, two alternative conduits have been employed: gluteraldehydestablized human umbilical vein (HUV) and polytetrafluoroethylene (PTFE). In this study of the 218 patients who underwent lower limb revascularization, 3-year patency of 85 SV graft was 75% compared to 34% for the 66 HUV grafts and 33% for the 67 PFTE grafts. Three factors were found to independently influence patency: the indication for surgery, the site of the distal anastomosis, and the angiographic runoff. The SV group had significantly better patency than either HUV or PFTE in each of these subgroups. No consistent difference between HUV and PTFE was found. A risk score was obtained by assigning a value of 1 to 3 for each of the factors influencing patency--indication: 1 = claudication, 2 = rest pain, 3 = ischemic lesions; site: 1 = above knee (AK), 2 = below knee (BK), 3 = tibial; runoff 1 = good (two or three vessels), 2 = fair (one vessel), 3 = poor (no vessel). Patients with the lowest risk scores (3 to 4) had the best 3-year patency: SV, 78%; HUV, 44%; and PTFE, 48%. Patients with the highest risk scores (7 to 9) had the worst 3-year patency: SV, 68%; HUV, 32%; and PTFE, 28%. SVs had better patency under high- and low-risk conditions and remain the conduit of choice for lower limb revascularization. Both HUV and PTFE have equivalent and acceptable patency when SV is unavailable or unstable.

Surgical procedures involving cardiopulmonary bypass in patients aged 70 or older.

Cardiac surgery was performed in 27 patients whose ages ranged from 70 to 78 years (mean, 72). In 17 of these patients, the operation was coronary artery bypass grafting without other procedures. There were 3 operative deaths (17.6 percent) but no late deaths during a mean follow-up period of 14 months, and all the 14 surviving patients were improved symptomatically. In the other 10 of the 27 patients, the operation was valve replacement. There was no operative mortality among the 6 aortic valve patients and 1 operative death among the 4 mitral valve patients; the corresponding late deaths were 2 and 1, respectively, during a mean follow-up period of 41.3 months. Improvements in operative management and improved criteria for the selection of patients should afford benefits and risks for elderly cardiac patients similar to those for younger cardiac patients.

Optimal myocardial protection.

The low mortality and perioperative infarction rates for aortocoronary bypass (ACB) make them unsuitable for evaluating the adequacy of myocardial protection. Enzymatic and functional measurements were found to be sensitive and specific indicators of myocardial injury. A prospective concurrent study of 78 patients undergoing triple ACB was conducted to evaluate the effectiveness of three popular methods of myocardial protection. Group I (32 patients) had a single dose of cold (4 degrees C) potassium cardioplegic (CPC) solution infused inducing a mean myocardial temperature (MMT) of 31 +/- 4 degrees C/min. Group II (23 patients) had multiple doses of CPC solution 8nducing a MMT of 22 +/- 2 degrees C/min. Group III (23 patients) had intermittent anoxic arrest at a MMT of 28 +/- 1 degrees C. The groups were not randomized but had comparable clinical symptoms and catheterization findings. Serial measurements of cardiac specific creatine kinase (CK-MB) revealed a peak in enzymatic activity occurring 60 minutes following ACB. The highest CK-MB was significantly (P less than 0.01) lower in group II (25 +/- 8 IU/liter) than group I (50 +/- 8 IU/liter), or group III (68 +/- 14 IU/liter). Myocardial performance was evaluated after ACB by serially measuring left ventricular stroke work index (SW) and left atrial pressure (LAP) in response to volume loading. The rise in SW was significantly (P less than 0.01) greater in group II (3.0 +/- 0.7 gm.m/sq m/mm Hg) than in group I (1.4 +/- 0.7) or group III (1.8 +/- 0.9). The highest SW attained was higher (P less than .01) in group II (43 +/- 7 gm.m/sq m) than group I (19 +/- 6) or group III (34 +/- 8) at comparable LAP values (group I: 20 +/- 5 mm Hg; group II: 18 +/- 3; group III: 18 +/- 4). Post-operative clinical evaluation failed to differentiate among the three groups. The more sensitive indices, however, demonstrated the superiority of cold, multidose cardioplegia in providing optimal myocardial protection.

Cardiac metabolism and performance following cold potassium cardioplegia.

The ability of cold potassium cardioplegia (CPC) to preserve cardiac metabolism and performance was evaluated in 68 patients undergoing anoxic arrest for aortocoronary bypass. Forty-five patients (group I) had a single dose of CPC inducing a mean myocardial temperature (MMT) of 32 degrees C/min. Twenty-three patients had multiple doses of CPC and systemic hypothermia to achieve a MMT of 22 degrees C/min. Arterial and coronary sinus sampling 38 minutes after aortic clamp removal permitted calculation of cardiac oxygen extraction, lactate production, CPK and CPK-MB release. Group I patients extracted less oxygen, produced more lactate, and released more CPK and CPK-MB. These indices of cardiac metabolism were found to correlate with anoxic times exceeding 30 minutes, and demonstrated more cardiac damage in group I patients at longer anoxic times. Serial measurements of cardiac output (thermodilution) and left atrial pressure during volume loading permitted construction of myocardial performance curves. Group I patients had a diminished response to volume loading postoperatively. Both the upslope and the highest stroke work attained were lower in group I and inversely related to the anoxic time. All patients made an uneventful recovery, indicating the insensitivity of clinical parameters of myocardial protection. Coronary sinus sampling and hemodynamic monitoring during volume loading permit an objective assessment of myocardial preservation.