Pronounced accumulation of metoprolol in ischemic myocardium after coronary venous retroinfusion

Combination of a calcium antagonist, a lipid-peroxidation inhibitor, and an angiotensin AT1-receptor antagonist provides additive myocardial infarct size-limiting effect in pigs

The calcium antagonist felodipine, the lipid-peroxidation inhibitor H290/51, and the angiotensin II type 1 (AT1)-receptor antagonist candesartan all exert beneficial effects on myocardial ischemia/reperfusion injury. This study was undertaken to test the hypothesis that a combination of these drugs with different pharmacologic properties could exert additive cardioprotective effects. Anesthetized pigs were subjected to 45 min of left anterior descending coronary artery occlusion followed by 240 min of reperfusion. Five groups of pigs were randomly given either 0.65 microM (7 nmol/kg) felodipine, 1.0 microM (3.1 microg/kg) H 290/51, 4.2 microM (20 microg/kg) candesartan, a cocktail of these three drugs, or vehicle (n = 6 for each) for 30 min starting at 5 min before reperfusion by coronary venous retroinfusion, which delivers drugs specifically to the ischemic regions. Systolic segment shortening (%SS) was measured by sonomicrometer. The myocardial area at risk and the final infarct size were determined by Evans blue and 2,3,5-triphenyl tetrazolium chloride staining. The hemodynamics did not change significantly during the study. In the vehicle group, the recovery of coronary flow was not maintained during reperfusion, and it was significantly lower after 240 min of reperfusion than during the preischemic period (p < 0.05). The coronary flow in the drug-treated groups was approximately the same by the end of the reperfusion period as that before the induction of ischemia. In the ischemic myocardium, %SS slightly recovered during reperfusion in the four drug-treated groups, but not in the vehicle group. The infarct size, expressed as a percentage of the myocardial area at risk, was smaller in all four drug-treated groups compared with the vehicle group. The infarct size in the cocktail group was significantly smaller than that in the groups given felodipine, H290/51, or candesartan alone. These results demonstrate that a combination of a calcium antagonist, a lipid-peroxidation inhibitor, and an angiotensin AT1-receptor antagonist has an additive effect on infarct limitation, indicating that combined therapy with agents having different pharmacologic modes of action may provide better cardioprotection than any of the drugs alone. The findings also support the view that reperfusion injury is possibly mediated by a combination of mechanisms.

Elimination, but not accumulation, of metoprolol by rat isolated perfused heart is selectively impaired by hypoxia

1. The influence of hypoxia on the time course of regional myocardial accumulation and elimination of the beta 1-adrenoceptor antagonist metoprolol was investigated by a spontaneously beating rat isolated perfused heart preparation. 2. Myocardial metoprolol content was maximal at 2 min in the left and right ventricles and atria. Neither the extent nor the time of maximal myocardial metoprolol content was significantly influenced by the induction of hypoxia. However, maximal myocardial metoprolol content in both atria and right ventricles was significantly higher than that in the left ventricular samples (P < 0.02; one-factor analysis of variance, 17 d.f.). 3. Elimination of metoprolol (as indicated from residual myocardial metoprolol content at 10 min) was impaired in hypoxic left ventricles (P < 0.01 vs normoxia; unpaired t-test, 10 d.f.) but not in right ventricles or atria. This variation in myocardial metoprolol disposition was not apparent from examination of serial metoprolol concentrations in coronary perfusate. 4. Hypoxia selectively impaired the elimination of metoprolol from the left ventricle, but not the process of drug accumulation, by any region of myocardium. It remains to be determined whether this reflects regional variation in the extent of microcirculatory impairment associated with hypoxia.

Retrograde infusion of lidocaine or L-arginine before reperfusion reduces myocardial infarct size

BACKGROUND

Retrograde perfusion preserves ischemic myocardium when initiated shortly after coronary artery occlusion. However, benefits diminish as the delay increases. In this study, we used this technique to deliver agents known to reduce the injury associated with the reperfusion of ischemic myocardium. We proposed that the local delivery of lidocaine or L-arginine before reperfusion would reduce the damage caused during reperfusion, even after a delay between onset of ischemia and intervention designed to approximate clinical reality.

METHODS

In a porcine model of myocardial ischemia, the left anterior descending coronary artery was snared immediately distal to its second diagonal branch. After 1 hour of occlusion, 34 animals were randomized into six groups: no intervention (control) (n = 6); administration of normal saline solution into the great cardiac vein (Retro-NS) (n = 6); administration of lidocaine either intravenously (i.v.-LID) (n = 6) or retrograde (Retro-LID) (n = 6); and administration of L-arginine either intravenously (i.v.-L-ARG) (n = 5) or retrograde (Retro-L-ARG) (n = 5). After 90 minutes of ischemia, the snare was released, and the myocardium was reperfused for 3 hours. Two-dimensional echocardiograms were made prior to occlusion and 60, 150, 210, and 270 minutes after occlusion. The infarct size and the area at risk were determined by lissamine green and triphenyltetrazolium chloride staining with computer planimetric quantification. Regional wall motion was assessed by a wall motion score: normal = 1; mild hypokinesia = 2.0; severe hypokinesia = 2.5; and akinesia = 3.

RESULTS

The area of the left ventricle at risk for infarction was similar in all groups and represented 25.4% (5.2% [standard deviation]) of the left ventricular mass (p = 0.63). The percent area of infarction in the area at risk after 3 hours of reperfusion was 76.7% (7.1% for the control group, 73.9% (5.7%) for the Retro-NS group, 72.1% (8.7%) for the i.v.-LID group, 54.5% (10.2%) for the Retro-LID group, 58.8% (4.0%) for the i.v.-L-ARG group, and 54.3% (4.0%) for the Retro-L-ARG group p < 0.005, Retro-LID and Retro-L-ARG versus Control, Retro-NS, and i.v.-LID; p < 0.03, i.v.-L-ARG versus control and Retro-NS). No significant difference in wall motion scores between groups was detected by echocardiography (p = 0.578).

CONCLUSIONS

Retrograde delivery of lidocaine or L-arginine before reperfusion reduces infarct size without acutely affecting wall motion after 90 minutes of ischemia and 3 hours of reperfusion. Lidocaine must be present before reperfusion to have an effect, whereas L-arginine is beneficial if it is delivered at the time of reperfusion.

Infarct size reduction with coronary venous retroinfusion of diltiazem in the acute occlusion/reperfusion porcine heart model

Calcium channel blockers are commonly used for the treatment of ischemic heart disease, but their effects on myocardial infarct size (IS) after reperfusion are not well known. Enflurane-anesthetized open-chest pigs subjected to 60-min left anterior descending coronary artery (LAD) occlusion followed by 3-h reperfusion were referred to one of the four experimental groups. Beginning 10 min before the onset of reperfusion, pigs in group A received diltiazem (7.5 micrograms/kg/min) retrogradely infused into the coronary vein for 30 min. In group B, the same amount of diltiazem was infused into the right atrium. A corresponding volume of saline was infused into the coronary vein in group C or into the right atrium in group D. IS expressed as a percentage of the myocardium at risk was significantly smaller (p < 0.01) in group A (33 +/- 14%; mean +/- SD) than in groups B (58 +/- 11%), C (58 +/- 11%), and D(63 +/- 10%). After reperfusion, functional recovery of the ischemic myocardium, determined by ultrasound crystals, was significantly more improved (p < 0.05) in group A as compared with other groups. The ischemic and nonischemic regional myocardial blood flow (RMBF), determined by radioactive microspheres, did not differ between four groups. Coronary venous retroinfusion of diltiazem had a myocardial protective effect in the porcine experimental model of acute coronary occlusion/reperfusion, whereas intravenous drug administration was not effective. The protective effect could not be attributed to washout of toxic metabolites from the ischemic area or to improved microcirculation. It was probably related to a pronounced accumulation of the calcium-channel blocker diltiazem in the ischemic myocardium achieved by the coronary venous route of delivery.

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.

Local beta-adrenergic blockade does not reduce infarct size after coronary occlusion and reperfusion: a study of coronary venous retroinfusion of metoprolol

Previous studies have demonstrated pronounced ischemic zone myocardial concentrations of metoprolol following coronary venous retroinfusion in pigs with coronary artery ligation. The effect of coronary venous retroinfusion of metroprolol on myocardial infarct size was studied in 16 pentobarbital-anesthetized open-chest pigs undergoing 60-minute occlusion of the left anterior descending coronary artery followed by 3 hours of reperfusion. Pigs in the experimental group (n = 8) were given 0.4 mg/kg (1.0 mg/ml) of metroprolol via the anterior interventricular vein over a period of 5 minutes, beginning immediately after coronary occlusion followed by 0.2 mg/kg/hr intravenously. Control pigs (n = 8) received the same volume of saline as the treated group. The risk area and the necrotic area were assessed by monastral blue dye and triphenyl tetrazolium chloride staining, respectively. Metoprolol did not influence hemodynamics. Plasma concentrations of metoprolol were within therapeutic levels. The administration of the beta-blocker resulted in a trend toward reduced norepinephrine concentrations, both in the aorta and coronary vein after coronary occlusion, but it did not prevent norepinephrine overflow following reperfusion. Infarct size expressed as a percentage of the risk area was 77 +/- 11% in the control group and 75 +/- 12% (mean +/- SD; NS) in the treated group. Thus, metoprolol retroinfusion did not reduce infarct size and did not prevent catecholamine overflow after reperfusion. It is concluded that the beneficial effects of metroprolol in acute infarction are probably unrelated to local beta-adrenergic blockade, at least in the pig, an animal with a paucity of coronary collateral blood flow.

Pharmacokinetic analysis of coronary sinus retroinfusion in pigs. Ischemic myocardial concentrations in the left circumflex coronary arterial area using metoprolol as a tracer

Myocardial availability of drug, using metoprolol as a tracer, in acutely ischemic myocardium in the area of the left circumflex (LCX) coronary artery was compared following standard intravenous (IV) administration and after coronary sinus retroinfusion. Seven open-chest farm pigs were subjected to a 21-minute occlusion of the LCX coronary artery. All animals received simultaneous IV tritium-labeled metoprolol (0.2 mg/kg) and unlabeled metoprolol (0.2 mg/kg) retrogradely into the coronary sinus. The drug administration was started after 1 minute of coronary artery occlusion and continued for 5 minutes. Intravenously administered metoprolol resulted in a higher peak plasma concentration of metoprolol (382 +/- 52 nmol/l) than coronary sinus retroinfusion (276 +/- 47 nmol/l). The nonischemic myocardial metoprolol concentration was of similar magnitude (393-454 pmol/g), whether infused IV or into the coronary sinus. Coronary sinus retroinfusion, however, resulted in a substantial accumulation of metoprolol in the ischemic myocardium (2887-5863 pmol/g). Coronary sinus retroinfusion resulted in a pronounced and specific accumulation in the ischemic myocardium in the territory of the LCX coronary artery.

Coronary venous retroinfusion of deferoxamine reduces infarct size in pigs

The efficacy of coronary venous retroinfusion of the iron chelator deferoxamine was studied in 24 pentobarbital-anesthetized open chest pigs with a 60 min occlusion of the left anterior descending coronary artery followed by 3 h of reperfusion. Eight retrogradely treated pigs were given 10 mg/kg body weight of deferoxamine by way of the anterior interventricular vein and eight systemically treated pigs received the same doses of deferoxamine intravenously. Drug infusions lasted for 5 min, beginning 15 min before reperfusion. Eight control pigs received systemic intravenous saline solution. Myocardial area at risk and necrotic area were assessed by the monastral blue dye and the triphenyltetrazolium chloride staining method, respectively. There were no significant differences in hemodynamics or regional myocardial function (sonomicrometry) among the groups. Infarct size expressed as percent of risk area was 73.9 +/- 13.5% in the control group, 70.6 +/- 16.4% in the systemically treated group and 48.5 +/- 21.4% (p less than 0.05) in the retrogradely treated group. In conclusion, deferoxamine significantly reduced infarct size after coronary occlusion only when given regionally by way of the coronary vein. Because there was no significant hemodynamic effect caused by deferoxamine infusion, it is suggested that this drug prevents postischemic reperfusion injury by a direct cardioprotective effect.

Pharmacokinetic analysis of coronary venous retroinfusion: a comparison with anterograde coronary artery drug administration using metoprolol as a tracer

Plasma and myocardial tissue concentrations of metoprolol were studied in ischemic and nonischemic areas of 22 pigs after 90 (n = 19) and 16 (n = 3) min of left anterior descending coronary artery occlusion. Group A (n = 6) received simultaneous intravenous metoprolol (0.2 mg/kg body weight) and tritium-labeled (3H)-metoprolol (0.2 mg/kg) retrogradely into the coronary vein. In group B (n = 5), metoprolol and 3H-metoprolol were administered in the same way, but at half the volume to study the influence of derived coronary venous pressure on the myocardial concentration of drug. In group C (n = 3), metoprolol was given retrogradely and saline solution was infused into the left anterior descending artery before induced death to wash out metoprolol from the coronary veins. To rule out a possible influence of the development of myocardial necrosis on drug distribution, metoprolol was retroinfused after 1 min of arterial occlusion in three pigs (group D). In group E (n = 5), metoprolol (0.2 mg/kg) was infused anterogradely into the left anterior descending artery. Peak plasma concentration was significantly higher after intravenous infusion of metoprolol (1,188 +/- 503 nmol/liter) than after coronary venous infusion (417 +/- 155 nmol/liter; p less than 0.001). In groups A and B, the nonischemic myocardial concentration of metoprolol was 250 to 300 pmol/g, whether the drug was infused intravenously or into the coronary vein. Coronary venous retroinfusion, however, resulted in a substantial accumulation of metoprolol in the ischemic myocardium. In group A pigs, subendocardial myocardial concentration was 16,800 +/- 7,774, mid-myocardial 39,590 +/- 18,043 and subepicardial 57,143 +/- 29,030 pmol/g (mean +/- SE). The ischemic myocardial concentration in pigs from group B was somewhat less pronounced, probably secondary to a lower coronary venous pressure (15 +/- 3 mm Hg) with the lower volume of infusion (6.1 +/- 0.3 ml) in group B compared with 32 +/- 5 mm Hg with a 14 +/- 1 ml infusion in group A. Coronary artery anterograde administration resulted in myocardial ischemic and nonischemic zone drug concentrations similar to those observed after retroinfusion into the coronary vein. With both modes of administration, there was a transmyocardial gradient from a somewhat lower drug concentration in the subendocardium, toward an increasing level in the mid-myocardium, to the highest concentration in the subepicardial zone of the ischemic myocardium. Coronary venous retroinfusion resulted in pronounced drug accumulation in the ischemic myocardium. The derived coronary venous pressure during infusion influenced the concentration of drug.(ABSTRACT TRUNCATED AT 400 WORDS)

Retrograde coronary venous administration of recombinant tissue-type plasminogen activator: a unique and effective approach to coronary artery thrombolysis

Recent studies of interventional therapy by way of the coronary venous system have demonstrated that it can protect acutely ischemic myocardium. To evaluate the efficacy of coronary venous retroinfusion compared with systemic intravenous administration of recombinant tissue-type plasminogen activator (rt-PA), 14 dogs were studied with a copper coil-induced thrombus in the left anterior descending coronary artery. The rt-PA (24,000 fluorescence units/kg) was administered continuously, either intravenously (n = 8) or retrogradely (n = 6), for 30 min beginning 60 min after coronary occlusion. Thrombolysis was determined by repetitive coronary angiography. All dogs were killed 3 h after termination of rt-PA infusion and infarct size was measured by the triphenyltetrazolium chloride staining technique. Complete thrombolysis occurred in five of the six dogs in the retroinfusion group and four of the eight dogs in the systemic intravenous infusion group. Partial lysis was achieved in two dogs treated by intravenous infusion. Lysis did not occur in one dog treated with retroinfusion and in two dogs treated with intravenous infusion. Time to thrombolysis was 13.4 +/- 2.3 min in the retroinfusion group versus 27.8 +/- 4.8 min in the intravenous group (p less than 0.001). Myocardial functional recovery in the ischemic zone measured by two-dimensional echocardiography 60 min after reperfusion was significant only in the retroinfusion group (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Positron emission tomography demonstrates that coronary sinus retroperfusion can restore regional myocardial perfusion and preserve metabolism

Positron emission tomography was used to image blood flow and metabolic tracers in risk zone myocardium after left anterior descending coronary artery occlusion during synchronized coronary venous retroperfusion. Six control and seven intervention open chest dogs had occlusion of the mid left anterior descending coronary artery. Synchronized retroperfusion commenced 25 min later. Flow tracers (rubidium-82 and nitrogen-13 ammonia) were injected retrogradely. Three hours after coronary occlusion, fluorine-18 (F-18) deoxyglucose uptake in the control and treatment groups was compared. At 200 min of occlusion, infarct size was assessed. Retrograde flow tracer uptake was observed in the risk zone in the seven intervention dogs. Fluorine-18 deoxyglucose uptake in the risk zone was increased in five of the six intervention dogs but was reduced in five of the six control dogs. The risk zone to normal zone F-18 deoxyglucose count ratio was higher in the intervention than the control group (1.13 +/- 0.39 vs. 0.59 +/- 0.51; p less than 0.05). The endocardial subsegment risk zone to normal zone F-18 deoxyglucose count ratio was also significantly higher in the intervention group. Percent infarction in the risk zone was 70% lower in the group treated with synchronized retroperfusion than in the control group (18.4 +/- 22.6% vs. 61.2 +/- 25.4%; p less than 0.02). Thus, positron emission tomography revealed that retroperfusion could deliver oxygenated blood and maintain metabolism in risk zone myocardium. Infarct size was limited to 30% of that of control. In acute closure of the left anterior descending coronary artery, synchronized retroperfusion might be considered for maintaining viability of the jeopardized myocardium if the artery cannot be reopened rapidly.