Assessment of Myocardium at Risk with Computerized Vectorcardiography and Technetium-99m-Sestamibi-Single Photon Emission Computed Tomography during Coronary Angioplasty

Objective - To compare the myocardium at risk (MAR) as estimated by computerized vectorcardiography (cVCG) with MAR determined by Tc-99m-sestamibi-SPECT using coronary angioplasty as the model for transient transmural ischemia in humans. Methods and results - In 37 patients with stable angina pectoris, cVCG was recorded continuously during coronary angioplasty. The scintigraphic defect was quantified using an automated software program (CEqual). The ST vector magnitude (ST-VM) and the ST change vector magnitude (STC-VM) correlated well with MAR estimated by scintigraphy, ST-VM ( r = 0.71, p < 0.001) and STC-VM ( r = 0.84, p < 0.001). All patients with STC-VM <50 &#119 V during occlusion had defects of less than 10% of the left ventricle. Conclusion - 1) ST-VM and STC-VM give a reasonable useful estimate of MAR size during transient coronary occlusion. 2) STC-VM <50 &#119 V is a reliable limit to identify patients with MAR size less than 10%. 3) ST-VM does not add information to STC-VM with respect to detection of ischemia. 4) The existence of collateral vessels has great impact on both ST-vector changes and scintigraphic imaging of myocardial ischemia.     

Assessment of myocardium at risk in pigs with single photon emission computed tomography and computerized vectorcardiography during transient coronary occlusion

Since myocardium at risk (MAR) is the major prognosticator of final infarct size and outcome in patients with acute myocardial infarction, it is highly desirable to estimate the size of the acutely ischemic myocardium, that is the MAR, in these patients. We assessed MAR size by Tc-99m-sestamibi-SPECT and computerized vectorcardiography using autoradiography as reference method. Transient myocardial ischemia was achieved in 12 pigs by coronary artery occlusion with PTCA catheters. During the procedure, computerized vectorcardiography was continuously recorded. After injection of Tc-99m-sestamibi and gadolinium-153-labelled microspheres, MAR size was estimated by SPECT and post-mortem autoradiography. Different cut-off levels (50-70%) were compared with respect to MAR-SPECT. Tc-99m-sestamibi-SPECT showed a good correlation with autoradiography (r = 0.94). Computerized vectorcardiography showed a good correlation with autoradiography as well as with Tc-99m-sestamibi-SPECT (STC-VM: r = 0.75 and 0.80, respectively, ST-VM: 0.75 and 0.87, respectively). It was found that 1) MAR assessed by Tc-99m-sestamibi-SPECT correlates closely with the autoradiographic reference; 2) a lower cut-off point of 60% of maximum uptake for MAR by Tc-99m-sestamibi-SPECT gives the closest correlation with the autoradiographic reference; and 3) ST-VM and STC-VM correlate well with MAR assessed by Tc-99m-sestamibi-SPECT and autoradiography.     

Assessment of Myocardium at Risk in Pigs with Single Photon Emission Computed Tomography and Computerized Vectorcardiography During Transient Coronary Occlusion

Since myocardium at risk (MAR) is the major prognosticator of final infarct size and outcome in patients with acute myocardial infarction, it is highly desirable to estimate the size of the acutely ischemic myocardium, that is the MAR, in these patients. We assessed MAR size by Tc-99m-sestamibi-SPECT and computerized vectorcardiography using autoradiography as reference method. Transient myocardial ischemia was achieved in 12 pigs by coronary artery occlusion with PTCA catheters. During the procedure, computerized vectorcardiography was continuously recorded. After injection of Tc-99m-sestamibi and gadolinium-153-labelled microspheres, MAR size was estimated by SPECT and post-mortem autoradiography. Different cut-off levels (50-70%) were compared with respect to MAR-SPECT. Tc-99m-sestamibi-SPECT showed a good correlation with autoradiography (r = 0.94). Computerized vectorcardiography showed a good correlation with autoradiography as well as with Tc-99m-sestamibi-SPECT (STC-VM: r = 0.75 and 0.80, respectively, ST-VM: 0.75 and 0.87, respectively). It was found that 1) MAR assessed by Tc-99m-sestamibi-SPECT correlates closely with the autoradiographic reference; 2) a lower cut-off point of 60% of maximum uptake for MAR by Tc-99m-sestamibi-SPECT gives the closest correlation with the autoradiographic reference; and 3) ST-VM and STC-VM correlate well with MAR assessed by Tc-99m-sestamibi-SPECT and autoradiography.     

Contributions of myocardial ischemia and heart rate to ST segment changes in patients with or without coronary artery disease

Background: ST changes related to ischemia at different heart rates (HRs) have not been well described. We aimed to analyze ST dynamic changes by vectorcardiography (VCG) during pacing-induced HR changes for subjects with proven coronary artery disease (CAD) and without (non-CAD).
Methods: Symptomatic CAD patients scheduled for elective surgery were enrolled along with a non-CAD group. During anesthesia, both groups were placed at multiple ascending levels. VCG ST data, and in particular in ST change vector magnitude (STC-VM) from baseline, along with arterial and great coronary artery vein (GCV) blood samples were collected to determine regional myocardial lactate production.
Results: A total of 35 CAD and 10 non-CAD patients were studied over six incremental 10 beat/min HR increases. STC-VM mean levels increased in the CAD group from 9±5 to 131±37 μV (standard deviation) compared with non-CAD subjects with 8±3–76±34 μV. Myocardial ischemia (lactate production) was noted at higher HRs and the positive predictive value for STC-VM to detect ischemia was 58% with the negative predictive value being 88%. STC-VM at 54 μV showed a sensitivity of 88% and a specificity of 75% for identification of ischemia.
Conclusions: Both HR and ischemia at higher HRs contribute to VCG ST elevation. Established ST ischemia detection concerning HR levels is suboptimal, and further attention to the effects of HR on ST segments is needed to improve electrocardiographic ischemia criteria.     

Early vectorcardiographic monitoring provides prognostic information in patients with ST-elevation myocardial infarction

OBJECTIVE: To evaluate the prognostic value of specified vectorcardiographic data obtained during the first hours of ST-elevation myocardial infarction for cardiac outcomes up to 5 years. DESIGN: Three hundred and five patients with ST-elevation myocardial infarction and chest pain for less than 12 h were monitored with continuous vectorcardiography. RESULTS: All patients had follow-up for at least 1 year. The mortality was 5.9% at 30 days and 10.8% at 1 year. The estimated 5-year mortality was 24%. A total of 7.9% had recurrent infarction at 30 days and 11.2% at 1 year. Recurrent infarction or death occurred in 12.1% at 30 days and in 19.7% at 1 year. The presence of ST-VM (plateau) >or= 125 microV was highly predictive of the combined endpoint death or recurrent infarction at 1 year, OR 2.69 (95% CI 1.39-5.23). Multivariate analysis showed that age >or=75 years, anterior myocardial infarction, and the presence of ST-VM (plateau) >or= 125 microV, were independently associated with increased risk of recurrent infarction or death at 1 year and with death at 5-year follow-up. A start value of ST-VM 相似文献   

The electrocardiographic reperfusion peak in patients with ST-elevation myocardial infarction

OBJECTIVES: To analyse the incidence and the prognostic value of the reperfusion peak in a population of patients with AMI treated with thrombolysis. DESIGN: Two hundred and sixty-nine patients with ST-elevation myocardial infarction treated with thrombolysis were monitored with continuous on-line vectorcardiography. RESULTS: A reperfusion peak defined as a transiently increased ST-VM of >50 microV followed by an immediate decrease to a level lower than the starting point was seen in 112 of all 269 (42%) patients and in 111 of 149 (75%) of the patients with successful ST-resolution. A reperfusion peak was an independent predictor of better prognosis both in the short- and the long term but had no implications on the prognosis in the subgroup with successful ST-resolution. CONCLUSION: A reperfusion peak was equally common in patients treated with thrombolysis having a successful ST-resolution as observed in studies of patients with successful primary coronary angioplasty. The reperfusion peak was associated with better prognosis and should be recognised as a possible marker of successful reperfusion but can mimic aggravated ischemia.     

Continuous vectorcardiography in cardiac surgery: natural course of vector changes and relationship to myocardial oxygen uptake

Continuous vectorcardiography was registered before and during the first 18 hours after cardiac surgery in 53 patients. QRS vector changes (QRS-VD) occurred during the operation, but no further changes were observed postoperatively. The ST vector (ST-VM) increased during the operation, and a further slight increase occurred postoperatively. Perioperative myocardial infarction occurred in three patients. Their ST-VM was higher than the average in patients without myocardial infarction, while QRS-VD did not differ from the average pattern. Twelve other patients were studied in pacemaker-induced moderate tachycardia. QRS-VD increased in proportion to heart-rate changes (rs median = 0.93, p less than 0.01). QRS-VD also correlated with myocardial oxygen uptake (rs median = 0.62, p less than 0.05). The ST-VM responses were not uniform. The data suggest that vectorcardiogram variables can provide information related to myocardial energy metabolism.     

Risk Stratification in Unstable Angina: How to Select Patients Who Need Emergency Revascularization

A bstract Patients considered to have unstable angina have a varying prognosis depending on their clinical presentation. Prognosis can be influenced by several factors including persistent pain, transient ST segment shifts, left main coronary artery stenosis, and silent myocardial ischemia. Most patients who present with unstable angina have their symptoms controlled initially with pharmacological management. If symptoms persist, coronary angioplasty or heart surgery can be performed but morbidity and mortality is slightly higher than in patients who are stable. Patients who will benefit from early revascularization include those with persistent myocardial ischemia as manifested by spontaneous angina, spontaneous ST segment shifts on ambulatory ECG, a positive exercise test at a low cardiac workload, or a markedly positive radionuclide or cardiac ultrasound imaging test.     

Prognosis of moderate coronary artery lesions in heart transplant patients.

BACKGROUND: Despite recent advances in our understanding of allograft vasculopathy, little is known about the evolution of moderate coronary lesions in heart transplant recipients. METHODS: We retrospectively analyzed 58 heart transplant patients undergoing annual coronary angiography who demonstrated a moderate lesion (>30% and <60% diameter stenosis) on any routine annual study. In an attempt to find criteria that could distinguish such patients who were at high risk of disease progression from those at low risk, we reviewed the clinical and biologic features and angiographic and clinical outcomes of patients with and without lesion progression at 1 year. RESULTS: Of the 58 patients who had an initially moderate coronary lesion, 28 (48%) showed progression of the lesion at angiography 1 year later (occlusion of the culprit vessel or progression to a severe lesion >60%) that required revascularization (angioplasty or bypass surgery). The 30 remaining patients showed no lesion progression. At the time of the first angiogram the only criterion which could predict lesion progression at 1 year was the presence of multi-vessel disease (p < 0.0001). Prognosis for these patients was poorer than in those with no disease progression, with a higher proportion of revascularization and sudden death (p < 0.001). Patients without lesion progression at 1 year had neither clinical events nor significant subsequent lesion progression during a mean follow-up of 6 years. CONCLUSIONS: The presence of a moderate coronary stenosis in heart transplant patients justifies a repeat angiogram 1 year later. The use of percutaneous coronary angioplasty in such patients has not been validated, but may be an option to delay or prevent progression to coronary occlusion.     

Effects of intracoronary shunts on coronary endothelial coating in the human beating heart

BACKGROUND: Local occlusion of coronary arteries during beating heart revascularization leads to injury of the arterial wall especially disturbing the integrity of the endothelium. The aim of this study was to elucidate the effects of intracoronary shunts versus local occlusion with elastic silicone loops on the beating heart in human coronary arteries by scanning electron microscopy. METHODS: Coronary arteries of patients with dilated cardiomyopathy (n = 4) or ischemic heart disease (n = 8) undergoing heart transplantation were locally occluded either with a silicone loop or with a shunt inserted after arteriotomy. Unmanipulated segments of the coronary arteries served as controls. Integrity of the endothelial lining was observed with scanning electron microscopy. RESULTS: Scanning electron microscopy revealed a statistically significant higher injury after shunting compared with controls (p < 0.001) and vessel loop occlusion (p < 0.001). There was no difference between both patient groups according to control specimens or after manipulation. CONCLUSIONS: From this investigation we conclude that insertion of intracoronary shunts during beating heart surgery leads to severe endothelial denudation in human coronary arteries. Therefore, at present we recommend using intracoronary shunts selectively in cases in which critical ischemia or technical difficulties as a result of anatomic conditions are expected during anastomosis and avoiding routine shunt insertion into coronary arteries during beating heart revascularization.     

Myocardial revascularization after failure of percutaneous transluminal coronary angioplasty

From 1980 to 1983, 299 procedures for percutaneous transluminal coronary angioplasty were performed in 265 patients. The procedure failed in 88 patients, 72 of whom underwent myocardial revascularization within 1 week following the angioplasty attempt. Operation on an emergency basis was required in 35 patients because of a major complication during or after coronary artery dilatation, whereas the remaining 37 patients underwent elective operation following failure without complication. Coronary occlusion occurred in 23 patients, coronary dissection without occlusion in four, perforation of the coronary artery in one patient, and no visible angiographic changes accounted for the severe myocardial ischemia in the remaining 7 patients. Signs of acute myocardial infarction were present preoperatively in 13 of the 35 patients (37.1%) who underwent emergent operation. Among the factors analyzed, only the absence of collateral circulation and the extent of coronary disease were directly related to the development of complications with percutaneous transluminal coronary angioplasty. There were no early or late deaths in this series. Postoperative complications occurred in seven patients (20%) of the group undergoing emergency operation and in none of the group having elective operation. New postoperative myocardial infarction developed in three patients (8.6%). In six of the 13 patients with preoperative evidence of necrosis, the electrocardiogram returned to normal without other signs of acute infarction after the operation, whereas myocardial infarction was complete in the remaining seven patients. Thus, patients who have complications from percutaneous transluminal coronary angioplasty should undergo immediate operation; for those in whom the procedure fails without complication, surgical treatment can be postponed and performed electively later on if indicated by the clinical incapacity of the patient.     

Continuous, Noninvasive, and Localized Microvascular Tissue Oximetry Using Visible Light Spectroscopy

Background: The authors evaluated the ability of visible light spectroscopy (VLS) oximetry to detect hypoxemia and ischemia in human and animal subjects. Unlike near-infrared spectroscopy or pulse oximetry (SpO2), VLS tissue oximetry uses shallow-penetrating visible light to measure microvascular hemoglobin oxygen saturation (StO2) in small, thin tissue volumes.

Methods: In pigs, StO2 was measured in muscle and enteric mucosa during normoxia, hypoxemia (SpO2 = 40-96%), and ischemia (occlusion, arrest). In patients, StO2 was measured in skin, muscle, and oral/enteric mucosa during normoxia, hypoxemia (SpO2 = 60-99%), and ischemia (occlusion, compression, ventricular fibrillation).

Results: In pigs, normoxic StO2 was 71 +/- 4% (mean +/- SD), without differences between sites, and decreased during hypoxemia (muscle, 11 +/- 6%; P < 0.001) and ischemia (colon, 31 +/- 11%; P < 0.001). In patients, mean normoxic StO2 ranged from 68 to 77% at different sites (733 measures, 111 subjects); for each noninvasive site except skin, variance between subjects was low (e.g., colon, 69% +/- 4%, 40 subjects; buccal, 77% +/- 3%, 21 subjects). During hypoxemia, StO2 correlated with SpO2 (animals, r2 = 0.98; humans, r2 = 0.87). During ischemia, StO2 initially decreased at -1.3 +/- 0.2%/s and decreased to zero in 3-9 min (r2 = 0.94). Ischemia was distinguished from normoxia and hypoxemia by a widened pulse/VLS saturation difference ([DELTA] < 30% during normoxia or hypoxemia vs. [DELTA] > 35% during ischemia).     

Transmyocardial laser induces coronary hyperemia and reduces ischemia-related arrhythmias, but fails to delay development of myocardial necrosis after coronary artery occlusion in pigs.

BACKGROUND: Several investigators have reported that transmyocardial revascularization (TMR) prior to acute coronary artery occlusion improves regional myocardial function and reduces the infarct size in animals with significant coronary collateral circulation. Whether the protective effect of TMR is due to perfusion through the laser-made channels, increased collateral flow or other mechanisms remains unresolved. The aim of this study was to investigate whether TMR performed prior to acute coronary artery occlusion could offer protection from ischemic injury in the pig, an animal with limited native collateral coronary circulation. METHODS: In one group (n=4), TMR was performed in the anterior wall of the left ventricle 30 minutes prior to occlusion of the proximal LAD for 45 minutes. The other group (n=6) was subjected to transient ischemia of the same duration without previous TMR. Area at risk and infarct size were determined after sacrifice. RESULTS: No significant difference was found in the infarct size between the two groups (69+/-2% in the TMR group versus 62+/-4% in the control group). However, the arrhythmic index during the period of ischemia was significantly lower in the TMR group (1.0+/-0.3 vs 8.3+/-2.2, p<0.001). Blood flow in LAD increased to a maximum of 135+/-6% of baseline level three minutes after the end of the TMR procedure. CONCLUSIONS: TMR failed to reduce the infarct size following acute coronary artery occlusion in the pig, an animal with a small collateral coronary flow capacity, but reduced ischemia-related arrhythmias and increased coronary flow transiently.     

Ischemic preconditioning during the use of the PercuSurge occlusion balloon for carotid angioplasty and stenting

Ischemic preconditioning (IP) uses transient ischemia to render tissues tolerant to subsequent, prolonged ischemia. This study sought to evaluate factors that contributed to the development of cerebral ischemia during PercuSurge balloon (Medtronic, Santa Rosa, CA) occlusion in patients undergoing carotid angioplasty and stenting (CAS). The PercuSurge occlusion balloon was used in 43 of 165 patients treated with CAS for high-grade stenosis; 20% were symptomatic. Symptoms of cerebral hypoperfusion during temporary occlusion of the internal carotid artery occurred in 10 of 43 patients and included dysarthria, agitation, decreased level of consciousness, and focal hemispheric deficit. The development of neurologic symptoms after initial PercuSurge balloon inflation and occluded internal carotid artery flow was associated with a decrease in the mean Glasgow Coma Scale (GCS) from 15 to 10 (range 9-14); the GCS returned to normal after occlusion balloon deflation. The mean time to spontaneous recovery of full neurologic function was 8 minutes (range 4-15 minutes). The mean subsequent procedure duration was 11.9 minutes (range 6-21 minutes). No recurrence of neurologic symptoms occurred when the occlusion balloon was reinflated. All 10 patients underwent successful CAS without occlusion, dissection, cerebrovascular accident, or death. Ischemic preconditioning can be used to enable CAS with embolic protection in patients who cannot tolerate initial interruption of antegrade cerebral perfusion by PercuSurge occlusion.     

Intraoperative ischemia and long-term events after minimally invasive coronary surgery

Background

Concern has been raised about the effects of prolonged left anterior descending (LAD) artery occlusion during minimally invasive direct coronary artery bypass graft surgery (MIDCABG). We sought to assess the impact of myocardial dysfunction during MIDCABG on long-term outcome and the protective role of collateral circulation on myocardial ischemia.

Methods

Myocardial function was evaluated in 92 patients by intraoperative transesophageal echocardiography during MIDCABG.

Results

Wall motion score index increased during LAD occlusion (p < 0.00l) and reverted after LAD reopening (p < 0.001 versus occlusion and p = not significant versus baseline). The change in wall motion score index (occlusion versus baseline) was higher in patients with multivessel disease (p < 0.05) and in patients with LAD Thrombolysis in Myocardial Infarction study classification flow grade 2 or less without collateral circulation (p < 0.05). Myocardial stunning was documented in 12 patients (13%). The 5-year adverse event rate (including death, myocardial infarction, and revascularization) was 12%. By multivariate Cox regression analysis, multivessel disease, but not perioperative ischemia or stunning, was the only predictor of event-free survival.

Conclusions

During MIDCABG anterior wall dysfunction is transient, with prompt recovery after completion of the anastamosis in most cases; myocardial stunning can be documented in a minority of patients. Flow either antegrade or retrograde in the LAD territory plays a protective role against the development of ischemia. Multivessel disease, but not perioperative ischemia or stunning, predicts long-term event-free survival.     

Surgical revascularization following failed percutaneous transluminal coronary angioplasty

Percutaneous transluminal coronary angioplasty (PTCA) was performed on 200 patients and failed in 36, 12 of whom underwent myocardial revascularization within 3 hours after the angioplasty attempt. Elective operations were performed without complications in the other 24 cases. The 12 emergency operations were necessitated by major complications during or after PTCA, viz, coronary occlusion (6 patients) coronary dissection (2) and failed catheter passage or dilation with severe myocardial ischemia (4). Three of these 12 patients had signs of acute myocardial infarction preoperatively, and new infarction appeared postoperatively in two cases. All eight patients with ST-segment elevation preoperatively had raised levels of myocardial enzymes postoperatively, and two of them had new Q-waves. Three of the 12 patients required inotropic drugs following revascularization. There was one postoperative death. When complications arise in PTCA, emergency operation should be undertaken. When PTCA fails, but without complications, surgery can be electively performed.     

Surgical management of acute myocardial ischemia following percutaneous transluminal coronary angioplasty. Role of the intra-aortic balloon pump

Acute myocardial ischemia is a serious complication of percutaneous transluminal coronary angioplasty, often requiring emergency myocardial revascularization. Since our initial report of 17 such patients, we have encountered an additional 32 patients requiring emergency myocardial revascularization since September, 1981. The indication for emergency myocardial revascularization was ischemic chest pain in all 32 patients. Percutaneous transluminal coronary angioplasty resulted in injury to the right coronary artery in 11 patients, the left anterior descending artery in 19 patients, and the left main artery in two patients. The onset of ischemia was immediate in 26 patients but delayed up to 22 hours in six patients. Chest pain was associated with ST-segment elevation in 21 patients, hypotension in 7 patients, and cardiac arrest in 6 patients. Immediate intra-aortic balloon pumping was instituted in the angioplasty suite in 16 patients. The mean time from onset of ischemia to completed revascularization was 156 minutes with a mean of 1.6 grafts performed per patient. Seventeen patients (53%) had enzyme evidence of myocardial infarction postoperatively, with a significantly higher (p less than 0.01) incidence of myocardial infarction in those patients with preoperative ST elevation (76% versus 9%). In the 21 patients with ST-segment elevation, the incidence of Q wave infarction was 20% (3/15) with balloon pumping and 50% (3/6) without balloon pumping. Complications associated with intra-aortic balloon pumping occurred in one patient (6%). There were no hospital or late deaths with follow-up extending 16 months. The spectrum of injury resulting from percutaneous transluminal coronary angioplasty extends from chest pain alone to severe transmural ischemia with hypotension or cardiac arrest. Presentation may be immediate or delayed. Urgent emergency myocardial revascularization remains the accepted therapy for this complication. Immediate preoperative intra-aortic balloon pumping is a useful adjunct to emergency myocardial revascularization in the group of patients with acute ischemia and ST-segment elevation.     

Effect of autonomic nervous system dysfunction on sudden death in ischemic patients with anginal syndrome died during electrocardiographic monitoring in Intensive Care Unit

AIM: The aim of this study was to investigate the role of sympathovagal imbalance in patients with 'ischemic' sudden death (arrhythmic death preceded by ST segment shift). Although heart rate variability is a powerful tool for risk stratification after myocardial infarction, the mechanism precipitating sudden death is poorly known. METHODS: We analyzed the records of 10 patients who had ischemic sudden death during ECG Holter monitoring. Thirty patients with angina and transient myocardial ischemia during Holter monitoring served as control subjects. Arrhythmias, ST segment changes and heart rate variability were analyzed by a computed interactive Holter system. RESULTS: In 8 patients the sudden death was induced by ventricular fibrillation; in 2 by atrioventricular block followed by sinus arrest. All 10 patients showed ST segment shift. ST depression (maximal change 0.54+/-0.16 mV) occurred in 6 patients and ST elevation (maximal change 0.65+/-0.24 mV) in 4. The standard deviation of normal RR intervals (SDNN) was 92+/-30 ms during total Holter monitoring period vs 70+/-10 ms and 46+/-8 ms in epoch 1 and epoch 2 respectively. The SDNN was lower before the occurrence of ischemic sudden death: 54+/-12 ms (P< 0.005) in epoch 3 and 26+/-5 (P<0.005) in epoch 4 (i.e. 5 min before the onset of fatal ST segment shift). In controls the SDNN was 108+/-30 ms during total Holter monitoring period, whereas is measured 58+/-28 ms 5 min before the most significant episode of ST shift vs 26+/-5 in the group with sudden death (P<0.001). CONCLUSION: Sympathovagal imbalance, as detected by a marked decrease in heart rate variability, is present in the period (5 min) immediately preceding the onset of the ST shift precipitating ischemic sudden death. These findings suggest that transient autonomic dysfunction may facilitate, during acute myocardial ischemia, fatal arrhythmias precipitating in sudden death.     

Perfusion-assisted direct coronary artery bypass provides early reperfusion of ischemic myocardium and facilitates complete revascularization

BACKGROUND: Perfusion-assisted direct coronary artery bypass (PADCAB) was developed to initiate early reperfusion of grafted coronary artery segments during off-pump operations to resolve episodes of myocardial ischemia and avoid its sequelae. This case series outlines intraoperative findings and clinical outcomes of our first year clinical experience with PADCAB. METHODS: From November 1999 to November 2000, 169 PADCAB and 358 off-pump coronary artery bypass procedures were performed at the Emory University Hospitals. The decision to use PADCAB was predicated on surgeon preference. Perfusion pressure and flow, amount of intracoronary nitroglycerin, and total perfusion time and volume were recorded at the time of operation. RESULTS: One off-pump coronary artery bypass patient required emergent conversion to cardiopulmonary bypass. Two PADCAB patients had ischemic ventricular arrhythmias during target vessel occlusion that resolved once active perfusion had begun. Perfusion pressure in PADCAB grafts was on average 44% higher than mean arterial pressure (p < 0.001). Nitroglycerin, infused locally by PADCAB, was used in 67 patients to resolve ischemic episodes and increase initial coronary flows. The mean number of diseased coronary territories and grafts placed was 2.8 +/- 0.5 and 3.4 +/- 0.7, respectively, in the PADCAB group, and 2.3 +/- 0.8 and 2.7 +/- 1.0, respectively, in the off-pump coronary artery bypass group (p < 0.001 for both comparisons). More PADCAB patients received lateral wall grafts than off-pump coronary artery bypass patients (83.4% vs 59.4%; p < 0.001). Hospital death and postoperative myocardial infarction were not different between groups. CONCLUSIONS: PADCAB can provide suprasystemic perfusion pressures and a means to add vasoactive drugs to target coronary vessels. PADCAB provides early reperfusion of ischemic myocardium and facilitates complete revascularization of severe multivessel coronary artery disease.     

Continuous, noninvasive, and localized microvascular tissue oximetry using visible light spectroscopy

BACKGROUND: The authors evaluated the ability of visible light spectroscopy (VLS) oximetry to detect hypoxemia and ischemia in human and animal subjects. Unlike near-infrared spectroscopy or pulse oximetry (SpO2), VLS tissue oximetry uses shallow-penetrating visible light to measure microvascular hemoglobin oxygen saturation (StO2) in small, thin tissue volumes. METHODS: In pigs, StO2 was measured in muscle and enteric mucosa during normoxia, hypoxemia (SpO2 = 40-96%), and ischemia (occlusion, arrest). In patients, StO2 was measured in skin, muscle, and oral/enteric mucosa during normoxia, hypoxemia (SpO2 = 60-99%), and ischemia (occlusion, compression, ventricular fibrillation). RESULTS: In pigs, normoxic StO2 was 71 +/- 4% (mean +/- SD), without differences between sites, and decreased during hypoxemia (muscle, 11 +/- 6%; P < 0.001) and ischemia (colon, 31 +/- 11%; P < 0.001). In patients, mean normoxic StO2 ranged from 68 to 77% at different sites (733 measures, 111 subjects); for each noninvasive site except skin, variance between subjects was low (e.g., colon, 69% +/- 4%, 40 subjects; buccal, 77% +/- 3%, 21 subjects). During hypoxemia, StO2 correlated with SpO2 (animals, r2 = 0.98; humans, r2 = 0.87). During ischemia, StO2 initially decreased at -1.3 +/- 0.2%/s and decreased to zero in 3-9 min (r2 = 0.94). Ischemia was distinguished from normoxia and hypoxemia by a widened pulse/VLS saturation difference (Delta < 30% during normoxia or hypoxemia vs. Delta > 35% during ischemia). CONCLUSIONS: VLS oximetry provides a continuous, noninvasive, and localized measurement of the StO2, sensitive to hypoxemia, regional, and global ischemia. The reproducible and narrow StO2 normal range for oral/enteric mucosa supports use of this site as an accessible and reliable reference point for the VLS monitoring of systemic flow.