Attenuation of myocardial ischemia during coronary occlusion by ultrashort-acting beta adrenergic blockade

Enhanced sensitivity of dobutamine stress echocardiography by observing wall motion abnormalities during the recovery phase after acute beta-blocker administration

Dobutamine stress echocardiography (DSE) has a modest sensitivity for detecting single-vessel coronary artery disease (CAD). This study assessed the additional diagnostic value of new or worsening wall motion abnormalities during recovery after acute administration of beta blockers. The study population consisted of 200 patients (mean 59 +/- 11 years of age, 144 men), who underwent DSE. Images were acquired at rest, low dose, peak dose, and during recovery. Patients received intravenous metoprolol (1 to 5 mg/min). The dose was adjusted to achieve a recovery heart rate within a 10% range of heart rate at rest. Coronary angiography was performed within 2 months. Inducible new wall motion abnormalities were observed in 168 patients (84%) at peak stress. An additional 14 patients (7%) developed new or worsening wall motion abnormalities during recovery. CAD was detected in 182 patients (86 had single-vessel CAD). Sensitivity, specificity, and accuracy of DSE were 88%, 65%, and 73% at peak stress and 97%, 65%, and 74% during recovery. Sensitivity was particularly higher during recovery than during peak stress in patients with single-vessel CAD (98% vs 81%, p <0.001). In conclusion, assessment of wall motion abnormalities during the recovery phase after acute beta blockade improves sensitivity of DSE, particularly in patients with single-vessel CAD.

Distal myocardial protection during percutaneous coronary intervention with an intracoronary beta-blocker

BACKGROUND

Experimental studies have demonstrated that intravenous beta-blocker administration before coronary artery occlusion significantly reduces myocardial injury. Clinical studies have shown that intracoronary (IC) propranolol administration before percutaneous coronary intervention (PCI) delays myocardial ischemia. The present study tested the hypothesis that IC propranolol treatment protects ischemic myocardium from myocardial damage and reduces the incidence of myocardial infarction (MI) and short-term adverse outcomes after PCI.

METHODS AND RESULTS

Patients undergoing PCI (n=150) were randomly assigned in a double-blind fashion to receive IC propranolol (n=75) or placebo (n=75). Study drug was delivered before first balloon inflation via an intracoronary catheter with the tip distal to the coronary lesion. Biochemical markers were evaluated through the first 24 hours and clinical outcomes to 30 days. Evidence of MI with creatine kinase-MB elevation after PCI was seen in 36% of placebo and 17% of propranolol patients (P=0.01). Troponin T elevation was seen in 33% of placebo and 13% of propranolol patients (P=0.005). At 30 days, the composite end point of death, postprocedural MI, non-Q-wave MI after PCI hospitalization, or urgent target-lesion revascularization occurred in 40% of placebo versus 18% of propranolol patients (hazard ratio 2.14, 95% CI 1.24 to 3.71, P=0.004).

CONCLUSIONS

IC administration of propranolol protects the myocardium during PCI, significantly reducing the incidence of MI and improving short-term clinical outcomes.

Value of rapid beta-blocker injection at peak dobutamine-atropine stress echocardiography for detection of coronary artery disease

OBJECTIVES

We studied the value of a rapid beta-blocker injection at peak dobutamine-atropine stress echocardiography (DASE) for the detection of coronary artery disease (CAD).

BACKGROUND

The presence of tachycardia and hyperdynamic wall motion may make it difficult to recognize a new wall motion abnormality (NWMA) at peak stress.

METHODS

We studied 101 patients (mean age 58.2 +/- 9.8 years) who underwent effective DASE and coronary angiography. All patients received a rapid intravenous injection of metoprolol immediately after peak DASE image acquisition. Positivity in combined peak plus post-metoprolol images was defined when there was only peak NWMA, maintenance of peak NWMA, or NWMA detected only after metoprolol injection. Significant CAD was defined as >or=50% stenosis by quantitative angiography.

RESULTS

There were 37 patients without and 64 with CAD. The sensitivity, specificity, accuracy, and positive and negative predictive values for the detection of CAD at peak stress were 84%, 92%, 87%, 95%, and 77%, respectively. Five patients with CAD had negative peak images that became positive only after metoprolol. Extension of peak NWMA during metoprolol was observed in 14 patients, and multivessel CAD was detected in 10 of them. The sensitivity, specificity, accuracy, and positive and negative predictive values for peak plus metoprolol images were 92%, 89%, 91%, 94%, and 87%, respectively.

CONCLUSIONS

The use of metoprolol injected at peak of dobutamine infusion improved the detection of CAD by DASE.

Esmolol in acute ischemic syndromes

BACKGROUND

beta-Blockers have been shown to reduce both morbidity and mortality rates in patients with acute coronary syndromes. However, because of potential side effects, their use is limited in patients who might benefit the most from such therapy. It was thought that the use of an ultra-short-acting intravenous beta-blocker might produce similar results with fewer complications in those patients with relative contraindications to beta-blocker therapy.

METHODS

Accordingly, we evaluated the use of esmolol in patients with acute coronary syndromes and relative contraindication to beta-blocker therapy in a prospective randomized trial. One hundred eight patients at 21 sites received an infusion of intravenous esmolol or standard therapy on admission and were followed for 6 weeks from the day of admission. The primary efficacy outcome was a composite event consisting of any of the following that occurred during the index hospitalization: death, myocardial (re)infarction, recurrent ischemia, or arrhythmia as well as silent myocardial ischemia assessed by ambulatory electrocardiographic monitoring. Safety end points including hypotension, bradyarrhythmias, new or worsening congestive heart failure, and bronchospasm were also recorded.

RESULTS

Event rates for primary end points were similar in the 2 groups: death (2% in the standard care group vs 4% in the group receiving esmolol), myocardial (re)infarction (4% standard vs 7% esmolol), ischemia (12% vs 13%), arrhythmias (4% vs 2%), and silent ischemia (13% vs 15%). There was a higher incidence of transient hypotension in the group receiving esmolol (2% vs 16%), but all such events were noted to resolve after discontinuation of the esmolol infusion. There were no additional differences in safety end points: bradycardia (2% for those receiving standard care vs 9% receiving esmolol), new congestive heart failure (10% vs 16%), bronchospasm (0% vs 7%), and heart block (2% vs 2%).

CONCLUSIONS

The use of an ultra-short-acting beta-blocker such as esmolol might offer an alternative to patients with contraindications to standard beta-blocker therapy. Although this trial had limited power to detect safety and efficacy differences between the 2 therapies, it was observed that safety end points, which occurred during esmolol administration, resolved readily when the infusions were decreased or discontinued. Additional testing is needed to substantiate these findings.

Esmolol protects the myocardium and facilitates direct version intracardiac operation with a beating heart

In recent years there has been renewed interest in beating heart surgery using the ultra-active and selective beta1-blocker, esmolol. However, there has not been a report of its use in direct version intracardiac surgery with beating heart. Twenty-four patients undergoing elective direct version intracardiac surgery (mitral valve replacement) were divided randomly into 2 groups: control group (normothermia cardiopulmonary bypass (CPB) direct version intracardiac beating heart surgery) and esmolol group (normothermia CPB direct version intracardiac beating heart surgery and intravenous esmolol drip during CPB to maintain heart rate at 30-50 beats/min). Steady hemodynamic parameters were maintained in both groups; however, the doses of dopamine used in control group were larger than those for the esmolol group (p<0.01). The myocardial ultrastructure was well maintained in both group, but the scores for myocardial mitochondria, glycogen grading and counting and the amount of adenosine triphosphate were higher in the esmolol group (p<0.05). There was no significant change in the malondialdehyde level in either group (p>0.05). Using esmolol in direct version intracardiac beating heart surgery protects the myocardium and facilitates the operation.

Intraoperative considerations during minimal-access cardiac surgery

The range of minimal-access cardiac surgery approaches has many implications in intraoperative management. A modified anesthetic regimen is required to deal with the type of surgical exposure, hemodynamic instability, whether cardiopulmonary bypass is used, and early extubation. Intraoperative considerations include hemodynamic monitoring, one-lung ventilation, pharmacological stabilization of the myocardium, pacing, hypothermia, bleeding, and rapid emergence with a minimum of postoperative mechanical ventilation. As a result, anesthetic methods and intraoperative management were modified to meet these specific needs of minimally invasive cardiac procedures.

Minimally invasive direct coronary artery bypass: anesthetic, monitoring, and pain control considerations

OBJECTIVE

Minimally invasive direct coronary artery bypass (MIDCAB) provides many anesthetic challenges including monitoring, managing myocardial ischemia, and pain control. The objective was to evaluate the monitoring requirements and the potential benefits of preischemic conditioning and intrathecal morphine sulfate in MIDCAB patients.

DESIGN AND SETTING

This review was retrospective and unrandomized and was conducted at Allegheny University Hospitals, Allegheny General, Pittsburgh, PA.

PARTICIPANTS

Sixty-four patients with single coronary artery lesions (> 70% obstruction) underwent attempted MIDCAB during a 1-year period between November 1995 and November 1996. Seven patients required conversion to conventional coronary artery bypass grafting (CABG) with cardiopulmonary bypass (CPB) and two patients required extended thoracotomy incisions. This report describes the remaining 55 patients who underwent MIDCAB.

INTERVENTIONS

Some of the MIDCAB patients received intrathecal morphine before anesthetic induction. Ischemic preconditioning was assessed in a subset of patients.

RESULTS

MIDCAB was performed in 55 of 64 patients. Transesophageal echocardiography (TEE) was used in all patients and a pulmonary artery catheter was used in 43% of patients. Esmolol was used in 25% of patients to reduce motion of the left ventricle (LV) during the left internal mammary artery (LIMA)-LAD anastomosis, but was used less often as the surgeons adapted to the use of a retractor that stabilized the ventricular wall adjacent to the site of the LIMA-LAD anastomosis. LAD occlusion caused reversible, regional systolic dysfunction by TEE in the anterior and apical LV segments. During LAD occlusion, nitroglycerin was used in 61% of patients and phenylephrine in 24%. Ischemic preconditioning did not prevent increases in systemic or pulmonary artery pressures during LAD occlusion. Most (85%) patients were extubated in the operating room. Intrathecal morphine decreased postoperative analgesic requirements. The mean hospital length of stay (LOS) was 4.0 +/- 1.7 days (range, 1 to 10 days).

CONCLUSIONS

MIDCAB may reduce hospital LOS for patients with single vessel coronary artery lesions when compared with median sternotomy with a LIMA-LAD graft performed on cardiopulmonary bypass. Pharmacologic heart rate control during the LIMA-LAD anastomosis is not critical with the use of a surgical retractor which diminishes ventricular motion. A single 5-minute test LAD occlusion did not protect against subsequent regional ischemic dysfunction in our subset of patients with normal baseline function.

Propofol attenuates ischemia-reperfusion injury in the isolated rat heart

The purpose of this study was to examine the direct effects of propofol on ischemia-reperfusion injury using an isolated Langendorff rat heart preparation. Hearts were perfused with Krebs-Henseleit (K-H) solution (control); intralipid; or 10, 30, and 100 microM propofol. Hearts were rendered globally ischemic for 25 min, then reperfusion was begun with K-H solution for 30 min. Treatment with 100 microM propofol delayed the onset of contracture during ischemia compared with control or intralipid treatments (6.4 +/- 2.1 vs 4.4 +/- 1.4 or 4.1 +/- 0.7 min, respectively; P < 0.05). During reperfusion, 100 microM propofol increased coronary flow and reduced lactate dehydrogenase release compared with control or intralipid treatments. After 30 min of reperfusion, left ventricular developed pressure (LVDP) returned to 55 and 76 mm Hg in the 30 and 100 microM propofol-treated groups, respectively, whereas LVDP was 39 mm Hg in the control group. The hearts treated with 100 microM propofol showed significantly lower left ventricular end-diastolic pressure compared with the control or intralipid groups 30 min after reperfusion (29 +/- 13 vs 48 +/- 5 or 48 +/- 11 mm Hg, respectively; P < 0.05). In histological evaluation, control and intralipid hearts had increased injury severity scores compared with hearts treated with 100 microM propofol (1.8 +/- 0.9 and 1.7 +/- 0.8 vs 1.0 +/- 0.7, respectively; P < 0.05). In conclusion, we suggest that propofol administered before and during global myocardial ischemia has cardioprotective effects on ischemia-reperfusion injury.

IMPLICATIONS

It is important to protect the heart from injury by ischemia and reperfusion. The current study demonstrates that in the isolated rat heart, propofol attenuates mechanical, biochemical, and histological changes causes by ischemia and reperfusion.

"Keyhole" coronary artery bypass surgery

OBJECTIVE

The objective of this study was to identify the utility of "keyhole" thoracotomy approaches to single vessel coronary artery bypass surgery.

SUMMARY BACKGROUND DATA

Although minimally invasive surgery is efficacious in a wide variety of surgical disciplines, it has been slow to emerge in cardiac surgery. Among 49 selected patients, the authors have used a left anterior keyhole thoracotomy (6 cm in length) combined with complete dissection of the eternal mammary artery (IMA) pedicle under thoracoscopic guidance or directly through the keyhole incision to accomplish IMA coronary artery bypass grafting (CABG) to the left anterior descending (LAD) coronary artery circulation or to the right coronary artery (RCA).

METHODS

Keyhole CABG was accomplished in 46 of 49 patients in which this approach was attempted. All patients had significant (> 70%) obstruction of a dominant coronary artery that had failed or that was inappropriate for endovascular catheter treatment (percutaneous transluminal coronary angioplasty or stenting). Forty-four of the 49 patients had proximal LAD and 5 had proximal RCA stenoses. The mean age of the patients (35 men and 14 women) was 61 years, and their median New York Heart Association anginal class was III. The mean left ventricular ejection fraction was 42%. Femoral cardiopulmonary bypass support was used in 9 (19%) of 46 patients successfully managed with the keyhole procedure. Short-acting beta-blockade was used in the majority of patients (38 of 46) to reduce heart rate and the vigor of cardiac contraction.

RESULTS

As 49 patients have survived operation, which averaged 248 minutes in duration. Median, postoperative endotracheal intubation time for keyhole patients was 6 hours with 25 of 46 patients being extubated before leaving the operating room. The median hospital stay was 4.3 days. Conversion to sternotomy was required in three patients to accomplish bypass because of inadequate internal mammary conduits or acute cardiovascular decompensation during an attempted off-bypass keyhole procedure Postoperative complications were limited to respiratory difficulty in three patients and the development of a deep wound infection in one patient. Nine (19%) of 46 patients received postoperative transfusion. There have been no intraoperative or postoperative infarctions, and angina has been controlled in all but one patient who subsequently had an IMA-RCA anastomotic stenosis managed successfully with percutaneous transluminal coronary angioplasty.

CONCLUSIONS

These early results with keyhole CABG are encouraging. As experience broadens, keyhole CABG may become a reasonable alternative to repeated endovascular interventions or sternotomy approaches to recalcitrant single-vessel coronary arterial disease involving the proximal LAD or RCA.

Antifibrillatory effect of esmolol alone and in combination with lidocaine

The primary objective of this study was to determine the effect of esmolol, administered alone and in combination with lidocaine, on ventricular fibrillation threshold (VFT) in pigs. A secondary objective was to determine the relationship between blood esmolol concentrations and VFT. We determined VFT using a train of electrical stimuli delivered to the right ventricle after eight paced beats at a basic cycle length of 285 ms. Current was increased in 2-mA increments until VF occurred. VFT determinations were performed during administration of esmolol 1,000 mu g/kg/min, during a continuous infusion of lidocaine, and during infusion of esmolol and lidocaine in combination. Mean increases in VFT from baseline during infusion of esmolol and lidocaine alone were 32.3 +/- 12.9 and 8.5 +/- 7.2 mA, respectively (p < 0.05, each drug compared with baseline; p < 0.05, esmolol vs. lidocaine). Mean increase in VFT from baseline during infusion of the combination was 52.0 +/- 22.0 mA (p < 0.05 as compared with baseline and with esmolol or lidocaine alone). The relationship between blood esmolol concentrations and VFT was described by a counterclockwise hysteresis curve, suggesting delay in equilibration of esmolol between blood and site of effect. The antifibrillatory efficacy of esmolol is significantly greater than that of lidocaine in this model. Administration of the two agents in combination resulted in significantly greater antifibrillatory efficacy than that associated with either drug administered alone.

Minimally invasive coronary artery bypass grafting: a new method using an anterior mediastinotomy

The benefit of internal mammary artery (IMA) grafting as a long-lasting intervention for coronary artery disease is well recognized. However, largely because they are less invasive, catheter based alternatives are frequently chosen, particularly to treat single or double vessel disease. To retain the advantages of the IMA graft, and to offset the invasiveness of conventional coronary artery bypass grafting, we developed a new minimally invasive method using an anterior mediastinotomy for treating left anterior descending (LAD) or right coronary artery disease, or both. Feasibility studies using 16 pigs and a human cadaver led to approval by the Institutional Review Board for use of this procedure to treat six patients (four men, two women; mean age, 63.8 +/- 13.6 [SD] yrs) who granted informed consent. Pedicle dissection of the IMA, using video assisted thoracoscopy if necessary, was made through a 2- to 3-inch horizontal anterior mediastinotomy. The underlying LAD artery was grafted during femoral vessel cardiopulmonary bypass, with cooling to 30 degrees C, induced ventricular fibrillation, and left ventricular venting if required. Transesophageal echocardiography performed after bypass showed that two patients maintained normal wall motion and four had improvement from the original impairment. One patient suffered a recurrence of angina 4 weeks after the procedure; recatheterization showed an acutely angled IMA, subsequently corrected by balloon angioplasty. The results of follow-up dobutamine echocardiographic stress tests were negative in all patients. With this minimally invasive approach, the procedure should provide the benefits of IMA grafting with shorter hospital stay, more rapid recovery, and less overall cost.

Absence of beneficial effect of intravenous metoprolol given during angioplasty in patients with single-vessel coronary artery disease

In a double-blind, randomized, placebo-controlled trial, the possible anti-ischemic effect of metoprolol during percutaneous transluminal coronary angioplasty was tested. Electrocardiograms, hemodynamics, and metabolism were studied in 27 patients with a stenosis in the left anterior descending coronary artery. Measurements took place before angioplasty, after each of four 1-minute occlusions and 15 minutes after the last balloon deflation. Patients were randomly given placebo or metoprolol (15 mg as a bolus intravenously, followed by an infusion of 0.04 mg/kg/hr). At the end of the procedure, the rate-pressure product had decreased by 15% (NS) and 23% (p = 0.001) in the placebo and metoprolol groups, respectively, mainly due to similar decreases in heart rate. Metoprolol tended to lower chest pain and reduce precordial ST-segment elevation due to angioplasty, but the effects were not statistically significant. Lactate, hypoxanthine, and urate release immediately after deflation was similar in both groups. Metoprolol reduced arterial plasma hypoxanthine throughout the procedure by about 30% (p < or = 0.02 vs. placebo). Thus, intravenous infusion of metoprolol did not significantly attenuate chest pain and ST-segment elevation, and failed to decrease cardiac lactate and oxypurine release. It did, however, reduce arterial hypoxanthine concentrations during angioplasty, possibly indicating that the beta-blocker inhibits extracardiac ATP catabolism.