Intraoperative internal mammary artery transit-time flow measurements: comparative evaluation of two surgical pedicle preparation techniques

Objects.

Myocardial revascularization is performed preferentially with internal mammary artery grafts. Pedicle preparation and pharmacologic vasodilatory treatment vary greatly. Objective measurements are difficult since peripheral and later coronary vascular resistance and possible competitive flow of the native bypassed coronary artery will influence the results significantly. Our objectives were: (1) measurement of internal mammary artery graft flow with the transit-time flow technique; (2) comparison of two surgical take-down techniques (skeletonizing vs standard pedicle preparation); (3) quantitation of transit-time flow compared to the free pedicle flow and (4) the vasodilatory effect of papaverine on internal mammary artery flow.

Method.

Consecutive elective cases of coronary artery bypass grafting, performed by two surgeons using routinely either skeletonizing of the internal mammary artery (group A, n=10) or classical pedicle preparation technique (group B, n=10), were studied prospectively. Anesthesia, cardiopulmonary bypass and operative data were otherwise comparable; likewise, hemodynamic parameters showed no statistical differences between the two groups. Transit-time flow (CardioMed, Medi-Stim, Norway) was measured at the following time points: beginning (1) and end of take-down (2); after papaverine soaking: before (3) and on cardiopulmonary bypass (4); free flow into a beaker (5); after anastomosis; on (6) and off cardiopulmonary bypass (7).

Results.

Measurement of mean flow showed the following results: (1) severe vasoconstruction of the internal mammary artery was detected in both groups regardless of the preparation technique (occurring earlier in group A); (2) papaverine soaking caused a moderate flow increase (up to 40%); (3) with corresponding cardiopulmonary bypass flow (4.4 vs 4.1 l/min in group B) a higher free flow in group A was evident (67.7 vs 50.7 ml/min); (4) after coronary grafting, transit-time flow showed no significant differences between the two groups and (5) using a 3 mm probe, a linear correlation was demonstrated between transit-time flow and simultaneously measured free flow (r=0.89).

Conclusion.

Intraoperative transit-time flow measurement is a reliable method for assessing internal mammary artery and coronary artery bypass flow; considering the simple technical application, the procedure may be regarded as a valuable instrument of quality control.     

Coronary heart disease risk factors in black and white patients with non‐insulin‐dependent diabetes mellitus

Objective. To determine possible racial differences in risk factors for coronary heart disease (CHD) in black and white patients with noninsulin‐dependent diabetes mellitus (NIDDM).

Methods: Study of risk factors for coronary heart disease among 308 subjects who met the WHO criteria for NIDDM.

Results. Both black and white patients were found to have a high prevalence of hypertension, obesity, low high density lipoprotein (HDL) cholesterol, low leisure‐time physical activity levels, and an atherogenic dietary profile. Black males were more likely to have hypertension, reported a greater intake of dietary cholesterol, and had lower triglycerides, higher HDL cholesterol levels, a lower CHOL/HDL ratio, and a lower waist to hip ratio (WHR) than white males. Black females had higher mean arterial and diastolic blood pressures, had lower triglycerides, higher HDL cholesterol, a lower CHOL/HDL ratio, a higher subscapular/triceps ratio and lower reported leisure‐time energy expenditure compared to white females. There were no racial differences found for obesity level.

Conclusion. Our results indicate that racial differences in CHD risk factors exist among black and white patients with NIDDM. The complex genetic, sociocultural and environmental interactions involving CHD risk factors that contribute to the development of CHD may eventually provide clues to the etiology of the disease.     

Evaluating the effectiveness of the coronary care nurses' role in smoking cessation

Summary

• ? The aim of this small-scale study was to assess the feasibility and impact of an individualized smoking cessation intervention among clients admitted to a coronary care unit with severe angina or a first time myocardial infarction.
• ? The intervention involved in-depth nursing assessment interviews related to client beliefs, motivation and experiences of smoking, culminating in an individualized cessation plan. Participants were offered follow up support during the first year post-intervention.
• ? The findings are highly encouraging with a 77% smoking cessation rate for surviving clients within the intervention group at the end of the first year, and with 75% continued successful smoking cessation amongst surviving clients 2 years post-intervention.

     

The mechanism of directional coronary atherectomy

An attempt was made to assess the mechanism of directional coronaryatherectomy using different methods of analysis. Quantitativecoronary angiography was used as the gold standard to assessthe immediate results of atherectomy, and a comparative quantitativeanalysis of atherectomy and balloon angioplasty was made. Todetermine whether the post-atherectomy cross-sectional areais close to a circle, we compared the area measurements obtainedby edge detection with those obtained by videodensitometry.Finally, the extent of a ‘Dotter’ effect was establishedby quantitative angiography following crossing the stenosiswith the atherectomy device. For the purpose of this study,the results of the first 113 successful atherectomy procedureswere reviewed. In matched lesions, directional atherectomy induceda greater increase in minimal luminal diameter than balloonangioplasty (1.6 mm vs 0.8 mm; P < 0.0001 However, this luminalimprovement is due to a substantial ‘Dotter’ effectinduced by the bulky atherectomy device. Following atherectomy,only a slight difference in cross-sectional area measurementsbetween edge detection and videodensitometry (mean difference:0.28 mm² was found. Histologic examination of an atherectomizedcoronary artery showed a near-circular post atherectomy areageometry. In conclusion, directional atherectomy is a very effectivedevice with a substantially better initial result than balloonangioplasty. However, insertion of this bulky device itselfcauses an important ‘Dotter’effect.     

Correlation of heterogeneous blood flow and fatty acid uptake in the normal dog heart

Summary Blood flow heterogeneity in normal myocardium may be caused by heterogeneous metabolic demand. We studied, from 80 tissue samples of the left ventricle (LV) of eight anesthetised, open-chest dogs (with prior -blockade (metoprolol) in four dogs), the radioactivity of²⁰¹Thalliumchloride (²⁰¹Tl), an indicator of blood flow, and of the fatty acid¹³¹-Iodine-heptadecanoic acid (¹³¹I-HDA), an indicator of metabolic demand, 3 min after intravenous injection. Global LV uptake (in percent of injected dose ×10^–2, per g tissue; mean ±SD) was 4.94±0.71 for²⁰¹Tl and 4.48±0.58 for¹³¹I-HDA in the dogs without -blockade, and 2.08±0.26 and 1.69±0.20, respectively, in dogs with -blockade (p<0.05). Beta-blockade thus decreased the fraction of cardiac output delivered to the LV, concurrently with a decreased heart rate and arterial blood pressure (p<0.05) and, thus, global metabolic demand and fatty acid uptake. Regional radioactivities per gram were normalized for mean LV radioactivities and heterogeneity was expressed as the coefficient of variation (CV). For pooled data (n=320) in dogs without -blockade, regional²⁰¹Tl and¹³¹I-HDA radioactivities varied from a factor of 0.1 to 1.6 and 0.3 to 1.8 of mean radioactivities, with a CV of 22.9 and 19.4%, respectively, and correlated (r=0.77, p<0.005). For pooled data (n=320) in dogs with -blockade, regional²⁰¹Tl and¹³¹I-HDA radioactivities varied from a factor of 0.2 to 1.5 and 0.2 to 1.6 of mean radioactivity and CV was 23.6% and 24.8%, respectively: r=0.92 (p<0.005). The endo/epi ratio for both radioactivities exceeded unity in each dog. In normal myocardium, blood flow and fatty acid uptake are thus heterogeneous, both transmurally and circumferentially, and matched, concomitantly with coupling of global blood flow to global metabolic demand and fatty acid uptake. This supports the idea that heterogeneous myocardial O₂ supply reflects heterogeneous metabolic demand.     

MRI in aqueduct compression and obstructive hydrocephalus due to an ectatic basilar artery

We describe a patient with an ectatic basilar artery in whom MRI showed marked indentation of the floor of the third ventricle and backward displacement of the midbrain, probably causing aqueduct stenosis. It appeared likely that the associated hydrocephalus was due not only to any water-hammer effect, but also to occlusion of the aqueduct.     

Partial Artificial Heart (ALVAD) Use with Subsequent Cardiac and Renal Allografting in a Patient with Stone Heart Syndrome

The abdominal left ventricular assist device (ALVAD) is an order of magnitude more effective than conventional intra-aortic balloon pumping (IABP) in unloading and providing circulatory support to the failing left ventricle. This is a report of a unique case which demonstrates that in the absence of pulmonary vascular obstruction or constriction, the ALVAD can substitute for both left and right heart function. A 21-year-old patient with a congenital bicuspid aortic valve developed acute valvular endocarditis which rapidly progressed to congestive heart failure. An operation was undertaken, the mitral and aortic valves were excised and replaced by porcine heterografts, and a fistula from the right sinus of Valsalva to the right ventricle was closed. When coronary circulation was restored, irreversible ischemic contracture of the left ventricle, or "stone heart" syndrome, developed and emergency ALVAD or partial artificial heart implantation was effected. This device functioned as a total artificial heart for nearly six days, while a donor heart was sought. The patient then underwent removal of the ALVAD and cardiac and renal allografting. The transplanted heart functioned well, but the patient expired fifteen days later from gram-negative sepsis.     

Central effects of paraoxon on haemodynamics in the cat

Summary Application of paraoxon into the left vertebral artery (8–80 g) or both the left and right vertebral artery (4–8 g) of the anaesthetized cat evoked dose-dependent depressor effects, whereas heart rate was not influenced significantly. Also after systemic administration of paraoxon (150–825 g·kg^–1), while peripheral muscarinic receptors were blocked, depressor effects were still observed. Dose-response curves for the depressor response to paraoxon were established. Infusion of low doses of dexetimide via the vertebral artery prevented the hypotensive action of paraoxon. The distribution of this antimuscarinic drug in the brain was investigated. The depressor effect of paraoxon can be attributed to both a decrease in peripheral resistance and cardiac output. Decerebration and midcollicular transection were carried out in order to elucidate the site and mechanism of action. The depressor effect of paraoxon seems to be mediated by a central mechanism of action located within the lower brain stem.It is concluded that stimulation of muscarinic receptors in the pontomedullary region gives rise to the observed changes in haemodynamic parameters. Muscarinic receptors in the hypothalamus seem to be of minor importance for the hypotensive action of paraoxon.     

The effect of a calcium channel antagonist,Nisoldipine, on the ischemia-induced change of canine sarcolemmal membrane

Summary Ischemic injury was produced in the dog heart by occluding the left anterior descending coronary artery just below the second diagonal branch for a duration of 1.5 h followed by the release of occlusion. Nisoldipine, 3.5 g/kg was injected intravenously 10 min before the occlusion and again 10 min before the commencement of reperfusion. The activity of serum creatine phosphokinase greatly increased after the reperfusion, and this increase was significantly suppressed by Nisoldipine. This drug, in addition, prevented ischemia-induced myocardial hemorrhage and premature ventricular contraction. Sarcolemmal membrane vesicles were prepared from an ischemic and non-ischemic portions of the myocardium 3 h after the commencement of reflow. The fraction was purified approximately 12-fold with respect to ouabain-sensitive (Na⁺K⁺)-ATPase as an indicator; contamination of mitochondria was minimum with cytochrome c oxidase as an indicator. Without treatment of Nisoldipine, the total amount of sarcolemmal phospholipid obtained from the ischemic area, as well as the amounts of phosphatidyl-choline and phosphatidyl-ethanolamine, were significantly decreased as compared with those obtained from the non-ischemic area. Nisoldipine treatment abolished the decrease in the sarcolemmal phospholipids, total as well as phosphatidyl-choline and-ethanolamine, induced by ischemia plus reperfusion. Therefore, our work indicates that the Ca⁺⁺ channel antagonist, Nisoldipine, suppresses the ischemia-induced increase in phospholipid breakdown of cardiac sarcolemma probably through its inhibitory effect on the Ca⁺⁺-mediated activation of membrane phospholipase, through its vasodilatory action, or both.     

The provocation of coronary arterial spasm in patients with recent transmural myocardial infarction

Provocative tests for coronary spasm were performed in a groupof 131 patients (124 men and 7 women) with recent (<6 weeks)transmural myocardial infarction. Coronary arteriography wasperformed 27±9 days after the onset of the infarction.The provocative test was performed using a single IV bolus of0.4 mg of ergometrine. Aortic pressure, ECG and arteriogramsof the two coronary vessels were repeated 3 and 5 min later.Provoked spasm was observed in 27 (21%) of the patients. In13 (48%) the coronary spasm occurred in a vessel presumed tobe responsible for the myocardial infarction, while it was observedin coronary artery unrelated to the area of the infarct in 14(52% of the cases with spasm). Thus, this study demonstratesa high degree of reactivity of the coronary tree of patientswith recent transmural myocardial infarction suggesting thelikelihood of a role for spasm in the infarction process andoffering some explanation for subsequent recurrent ischemicevents.