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Abstract

Background:

Some studies have suggested that certain Chinese herbal remedies and acupuncture could limit ischemia/reperfusion damage. We sought to determine whether the commonly used single herb Danshen (DS), either alone or in combination with Jiang Xiang (JX), or electroacupuncture (EA) reduces myocardial infarct size.

Methods:

An anesthetized rat model of proximal left coronary artery occlusion (30 minutes) and reperfusion (180 minutes) was used to measure infarct size (triphenyltetrazolium chloride) and ischemic risk zone (blue dye technique). Rats were either untreated (saline) or received an infusion of DS or DS + JX, starting 30 minutes prior to coronary occlusion. In a separate protocol, rats were untreated, received static needle (ND) placement without stimulation or EA at P5-P6 acupuncture points in the rat forearm starting 5 minutes before occlusion and lasting for 40 minutes, or starting 30 minutes before occlusion and lasting for 90 minutes.

Results:

In the herbal experiments, myocardial infarct size expressed as a fraction of the ischemic risk zone was 0.43 ± 0.06 in controls, 0.39 ± 0.05 in the DS group, and 0.42 ± 0.04 in the Danshen + JX groups (P = not significant [NS]). In the acupuncture study, there was no significant difference in infarct size as a fraction of the risk zone among the control group (0.38 ± 0.04), the ND group (0.47 ± 0.04), or the EA group (0.32 ± 0.05). When EA was started 30 minutes prior to coronary occlusion and continued for 30 minutes into reperfusion, infarct size was 0.41 ± 0.07 in controls and 0.38 ± 0.10 in EA (P = NS). Neither herbs nor EA altered heart rate or blood pressure. In a separate study of 5 minutes of coronary occlusion plus reperfusion, EA failed to reduce ventricular arrhythmias.

Conclusion:

Our studies do not suggest a cardioprotective effect of DS or DS + JX or EA in an experimental model of myocardial ischemia/reperfusion.

Keywords

alternative medicine herbs acupuncture Chinese herbs myocardial infarction arrhythmias

Introduction

Despite recent advances in the treatment of acute myocardial infarction, including early reperfusion with percutaneous coronary intervention or thrombolytic therapy, morbidity and mortality remain a significant burden.¹ New therapies that can be administered safely along with reperfusion to limit ischemia/reperfusion are needed. The hope is that such adjunctive therapy will limit myocardial infarct size above and beyond reperfusion alone.² There has been recent interest in combining alternative Eastern therapies with standard Western therapies. There are several Chinese herbs that are described to have cardiovascular protective effects. Danshen (DS; derived from salvia miltiorrhiza) is commonly used for angina and acute coronary syndromes as well as stroke in China.^3
–5 Danshen is thought to improve the microcirculation, dilate coronary arteries, suppress thromboxane formation, and limit myocardial ischemia/reperfusion damage.^3,4 In addition, DS reduces acetylated low-density lipoprotein uptake by macrophages⁵ and components of DS stimulate nitric oxide production by endothelial cells,⁶ suggesting that it may have favorable effects on the modulation of atherosclerosis.⁷ Another popular mixture of herbs administered to coronary artery patients in China is the mixture of DS + Jiang Xiang (JX).⁸ Jiang Xiang (Dalbergia odorifera) contains flavinoids that protect against oxidative injury and has angiogenic properties.^9,10 However, whether these herbal products reduce anatomic infarct size in systematic models of myocardial infarct size remain unclear.

Another promising alternative therapy for coronary artery disease is acupuncture.^11,12 Li et al showed that electroacupuncture (EA) reduces sympathetic outflow, particularly through its action on premotor sympathetic neurons in the brain stem and reduces myocardial ischemia by decreasing oxygen demand rather than by improving supply.¹³ Pretreatment with EA for several days reduced cardiac arrhythmias and infarct size in the rat.^11,14,15 However, for the treatment of acute myocardial infarction in the clinical setting, several days of pretreatment would not be feasible due to the unpredictable nature of the onset of myocardial infarction. Therefore, we tested the hypothesis (1) that acute administration of DS or the mixture of DS + JX would reduce the size of experimental myocardial infarction in a rat model of coronary artery occlusion (CAO)/reperfusion, (2) that bilateral EA at Neiguan (P6) + Jianshi (P5) acupoints (P referring to pericardial meridian) could acutely reduce myocardial infarct size, and (3) that EA reduces reperfusion-induced arrhythmias in a rat model of ischemia/reperfusion unassociated with the development of tissue necrosis.

Methods

Protocol 1: Effect of Herbal Medicines on Myocardial Infarct Size

Adult female Sprague Dawley rats (average body weight ∼235 g) were anesthetized with ketamine (75 mg/kg) and xylazine (5 mg/kg) by intraperitoneal injection. The neck and chest were shaved. Rats were transferred to a heating pad, intubated, and connected to a rodent respirator. A rectal thermometer was inserted for monitoring core body temperature. A fluid-filled catheter was inserted into the right carotid artery for monitoring heart rate and blood pressure. The left jugular vein was then cannulated with a fluid-filled catheter for the later administration of blue dye (for risk zone determination) and potassium chloride (for euthanasia). A left thoracotomy was performed at the fourth intercostal space. After excising the pericardium, a 4-0 silk suture was passed under the coronary artery and threaded through a piece of tubing creating a snare to be used for CAO. Standard limb lead II of the electrocardiogram (ECG) was then positioned accordingly. A stabilization period of 10 minutes following the surgical preparation was allowed, and the animals randomized into one of the 3 groups: group 1 (control, [CN])—infusion of saline; group 2 (DS)—infusion of 0.675 g/kg; and group 3 DS + JX infusion of 0.8 + 0.8 g/kg. The herbs were imported from China as prescription-grade preparations, kindly provided by Dr Hongjie Zhang of China. Danshen was made by Anhui Tianyang Pharmaceutical Company (Anhui, China); the combination of DS and JX was made by Kunming Xingz-hong Pharmaceutical Company (Kunming, China). The dose was derived from a previous study demonstrating a beneficial effect on myocardial infarct size in the rat model.¹⁶

After randomization, another catheter, prefilled with CN, DS, or DS + JX, was then inserted into a side branch of the left jugular vein and connected to an infusion pump. Infusion began 30 minutes prior to CAO and continued throughout a 30-minute period of occlusion (total duration: 1 hour; total volume = 3 mL). At the end of the occlusion, the snare was released, and reperfusion of the coronary artery was maintained for 180 minutes. Additional anesthesia was administered intraperitoneally as needed to maintain a surgical depth of anesthesia.

Heart rate, mean systemic arterial blood pressure, body temperature, and standard limb lead II of the ECG were monitored throughout the study. Measurements were recorded at baseline, 1 minute prior to CAO occlusion, 29 minutes into CAO occlusion, 30 minutes into reperfusion, and at 179 minutes of reperfusion.

At the end of the reperfusion phase, the artery was reoccluded and blue dye (0.6 mL) was injected into the jugular catheter to delineate the previously ischemic area (ischemic risk zone = nonblue area) from the nonischemic portion (blue) of the left ventricle (LV). Under deep anesthesia, KCl (0.6 mL) was then administered through the same catheter to euthanize the rat. The heart was excised and the right ventricle and great vessels removed. The heart was sliced transversely into 4 slices from the apex to the base. The slices were photographed using a digital camera to delineate the ischemic risk zone. Heart slices then were incubated in triphenyl tetrazolium chloride (TTC) for 15 minutes to delineate the infarct (white or pale yellow tissue),¹⁷ rephotographed, weighed, and placed in formalin. The area at risk (AR) and area of necrosis (AN) were determined by digitized planimetry (Image J, from National Institutes of Health, Bethesda, Maryland; http://rsb.info.nih.gov/ij/). In the first pictures, the nonischemic section of the LV of each slice is represented by the blue area. The ischemic area is the unstained (pink) section of the slice. After incubation in TTC, the viable tissue was stained brick red, and the necrotic tissue appeared white. Using the planimetry software, the areas were measured and multiplied by the weight of each slice (respective to the area measured), to obtain the total AR and total AN. The AR was expressed as the fraction of the LV. Myocardial infarct size was expressed as the AN as a fraction of the AR (AN/AR).

Exclusion criteria were rats with a mean arterial pressure of <60 mm Hg after the stabilization period; failure to complete the study; hearts with an AR <25% of the LV. A total of 46 rats were entered into this study and 12 were excluded. The primary end point of the study was myocardial infarct size expressed as AN/AR.

Protocol 2A: Effect of Electroacupuncture on Myocardial Infarct Size

Adult female Sprague Dawley rats (average weight 263 g) were anesthetized with ketamine (75 mg/kg) and xylazine (5 mg/kg) injected directly into the peritoneum. The same surgical preparation as described in protocol 1 was utilized to induce acute myocardial infarction. Standard limb lead II of the ECG was monitored. A stabilization period of 10 minutes following the surgical preparation was observed, during which animals were randomized into one of the 3 groups: (1) needle insertion without stimulation (static needle [ND]); (2) electroacupuncture (EA); or (3) control (CN, no intervention). Additional anesthesia was administered throughout the protocol as required to maintain surgical depth.

For animals randomized into ND and EA, 12 minutes before CAO, acupuncture needles were applied bilaterally at P5 and P6 acupuncture points in the rat fore legs. To ensure proper locations of the needles, they were stimulated briefly (<60 seconds) at 1 to 4 mA and 2 to 4 Hz, and stimulus duration of 0.5 milliseconds and the motor threshold response of the rat paw (movement of the paw) were verified. These stimulation parameters for low frequency EA are known to activate both groups III and IV afferent fibers and to provide input to cardiovascular regions of the brain stem that regulate autonomic outflow.^13,18,19 The ND group then received ND placement without electrical stimulation. The EA was started 5 minutes before CAO. The needles were stimulated at the same intensity and frequency as stated previously. The EA was continued throughout CAO and continued for 5 minutes into reperfusion (total duration = 40 minutes). Electroacupuncture was discontinued after 5 minutes of reperfusion and the needles removed from the ND and EA rats. A waiting period of 12 minutes in the CN group was observed prior to CAO. All rats received 30 minutes of CAO. At the end of occlusion, the snare was loosened and the coronary artery was reperfused for 120 minutes.

Following reperfusion, the artery was reoccluded and blue dye (0.6 mL) injected into the jugular catheter to delineate the previously ischemic area from the nonischemic portion of the LV. Under deep anesthesia, KCl (0.6 mL) was then administered through the same catheter to euthanize the rat. The same procedures were utilized to delineate the AN, AR, and AN/AR as described in protocol 1.

Heart rate, mean arterial blood pressure, ECG lead II, and body temperature were monitored continuously during the study. These parameters were recorded at baseline (prior to needle insertion), 1 minute prior to coronary occlusion, 29 minutes into coronary occlusion, and at 30, 60, and 119 minutes of reperfusion.

Exclusion criteria were the same as in protocol 1. A total of 42 rats entered the study and 6 rats were excluded. The primary end point of this study was AN/AR.

Protocol 2B: Effect of 30 Minutes of Preocclusion Acupuncture on Myocardial Infarct Size

The same basic surgical preparation was utilized as in protocol 2A. Rats were randomized into either a control group (30-minute waiting period; no needles) or EA group in which EA was begun 30 minutes prior to coronary occlusion, continued through 30 minutes of coronary occlusion, and then stopped at 30 minutes after reperfusion. Hence, EA was administered for a total of 90 minutes. The proximal left coronary artery was occluded for 30 minutes followed by 120 minutes of reperfusion. The AR, AN, and AN/AR were measured as described above; and the same exclusion criteria were applied as in protocol 2A. A total of 18 rats were entered into this study and 7 were excluded. The primary end point was myocardial infarct size expressed as AN/AR.

Protocol 3: Effect of Acupuncture and Reperfusion—Induced Arrhythmias in a Non-Necrotic Model

Since EA has been suggested to benefit arrhythmias,^12,15 we determined whether arrhythmias were reduced by EA in a reliable model of ischemia/reperfusion arrhythmias that is independent of infarction.^20

–23 We have utilized a pentobarbital anesthetized rat model of 5 minutes of CAO/5 minutes reperfusion to demonstrate the antiarrhythmic properties of preconditioning, postconditioning, ranolazine, and other antiarrhythmic agents.^20

–23 A brief period of ischemia/reperfusion²⁰ does not cause infarction, so any benefit of an agent upon arrhythmias is unrelated to its action on tissue necrosis.

Adult female Sprague Dawley rats (average weight 264 g) were anesthetized with sodium pentobarbital (40 mg/kg) injected directly into the peritoneum. The remainder of the surgical preparation was the same as described in protocols 1 and 2. Standard limb lead II of the ECG was monitored. A stabilization period of 10 minutes following the surgical preparation was observed, during which the animals were randomized into one of the 2 groups: (1) control (no intervention) and (2) EA. Needles were applied bilaterally at the P5 and P6 points in the rat foreleg, 40 minutes before CAO in the EA group. EA was initiated 30 minutes before CAO by stimulating the needles with a current of 1 to 4 mA at a frequency of 2 to 4 Hz. Since EA was initiated 30 minutes prior to the 5 minute CAO and ended at the termination of the 5 minute reperfusion phase of the study, the total duration of EA was 40 minutes. We established a 40-minute wait period (to parallel the placement of needles in the treated group) prior to occlusion in the controls of group 1. The coronary artery was occluded for 5 minutes in both the groups. Then the snare was released and the artery was reperfused for 5 minutes.

Heart rate, mean blood pressure, ECG, and body temperature were recorded continuously. During the first 5 minutes of reperfusion, the ECG was analyzed for arrhythmias (see below).

The artery was reoccluded and blue dye (0.6 mL) was injected into the jugular catheter at the end of the reperfusion to delineate the previously ischemic area from the nonischemic portion of the LV. KCl (0.6 ml) was then administered under deep anesthesia through the same catheter to euthanize the rat. The AR was determined as described in protocol 1.

Exclusion criteria were the same as in protocols 1 and 2. A total of 15 rats were entered into this study and 5 rats were excluded.

End Points

Quantitative analysis of arrhythmias included the presence of any arrhythmia, including ventricular tachycardia (VT), ventricular fibrillation (VF), ventricular premature beats (VPB); onset of VT after reperfusion; total number of VT episodes; total duration of VT episodes; any episodes of sustained VT (VT of 10 seconds or more); total number of sustained VT episodes; total duration of sustained VT episodes; any episodes of VF; total duration of episodes of VF; any VPBs; and total number of VPBs.

Statistical Analyses

Data were calculated and tabulated using Excel work sheets. All data summary and statistical analyses were performed using SAS (Version 9.3, Cary, North Carolina). Body weights, left ventricular weights, risk zone, and infarct size were compared using analysis of variance. Changes in hemodynamic variables over time were analyzed by repeated measures of analysis of variance. If an F < 0.05 was obtained for the model, differences among means were determined by the method of contrasts. Analysis of covariance was used to test for a group effect on the regression model of necrotic myocardium with risk zone. Data are expressed as means ± standard error of the mean (SEM). For arrhythmias, the presence or absence of arrhythmias were analyzed by Fisher exact test and of arrhythmias quantified by the Kruskal-Wallis test. Arrhythmias are expressed as both medians and means.

Results

Protocol 1: Effect of Herbal Medicines on Myocardial Infarct Size

The AR (expressed as a fraction of the LV) was similar among the 3 groups at 0.54 ± 0.03 (mean ± SEM) in the CN (n = 11) group, 0.50 ± 0.03 in the DS (n = 11) group, and 0.49 ± 0.03 in the DS + JX (n = 12) group (P = not significant [NS]; Figure 1A). Myocardial infarct size expressed as a fraction of the risk zone was 0.43 ± 0.06 in the control group, 0.39 ± 0.05 in the DS group, and 0.42 ± 0.04 in the DS + JX group (P = NS; Figure 1B). The AN of the LV correlated with the AR (r = .59; P = .0003), but there was no group effect (Figure 1C).

Figure 1.

Chinese herbs. A, Ischemic risk region (expressed as a fraction of the left ventricle) in control (CN, grey), Danshen (DS, black), and combined Danshen and Jiang Xiang (DS+JX, white) groups. B, Effect of herbs on myocardial infarct size (expressed as a fraction of the risk region). C, Correlation between necrosis (fraction of LV) and risk zone (fraction of LV). D, Heart rate and mean blood pressure. bpm, beats per minute; BP, blood pressure; occl, occlusion; rep, reperfusion.

Heart rate was 223 ± 8 in controls, 225 ± 11 in DS, and 210 ± 9 beats/minute in DS + JX at 29 minutes into coronary occlusion. Heart rate gradually increased throughout the study without a group effect (Figure 1D). Mean blood pressure (mm Hg) was 63 ± 3 mm Hg in controls, 63 ± 3 in DS, and 72 ± 3 in DS + JX after 29 minutes of coronary occlusion (P = NS). Blood pressure tended to fall throughout the experiment without a significant group effect (Figure 1D).

Protocol 2A: Effect of Acupuncture on Myocardial Infarct Size

The AR, expressed as a fraction of the LV, was similar among the 3 groups (n = 12 for each group) at 0.45 ± 0.03 (mean ± SEM) in the CN group, 0.41 ± 0.03 in the EA group, and 0.47 ± 0.02 in the ND group (P = NS; Figure 2A). Myocardial infarct size expressed as a fraction of the risk zone was 0.38 ± 0.04 in the CN group; 0.32 ± 0.05 in the EA group, and 0.47 ± 0.04 in the ND group (P = .07; Figure 2B). There was a modest correlation between AN (fraction of LV) and AR (fraction of LV) at r = .37; P = 0.03; but no significant group effect (Figure 2C). Electroacupuncture did not alter heart rate or blood pressure (Figure 2D).

Figure 2.

Electroacupuncture. A, Ischemic risk region (expressed as a fraction of the left ventricle) in control (CN, grey), needles alone (ND, black), and electroacupuncture (EA, white) groups. B, Effect of electroacupuncture on myocardial infarct size (expressed as a fraction of the risk region). C, Correlation between necrosis (fraction of LV) and risk zone (fraction of LV). D, Heart rate and mean blood pressure. bpm, beats per minute; BP, blood pressure; occl, occlusion; rep, reperfusion.

Protocol 2B: Effect of 30 Minutes of Preocclusion Acupuncture on Myocardial Infarct Size

The AR (expressed as a fraction of the LV) was similar among the 2 groups at 0.40 ± 0.03 in the control group (n = 5) and 0.42 ± 0.05 in the EA group (n = 6: P = NS). Myocardial infarct size expressed as a fraction of the risk zone was 0.41 ± 0.07 in the control group and 0.38 ± 0.10 in the EA group (P = NS). EA did not influence heart rate, blood pressure, or temperature.

Protocol 3: Effect of Acupuncture- and Reperfusion-Induced Arrhythmias in a Nonnecrotic Model

The AR (fraction of the LV) was similar between the 2 groups (n = 5 for each group) at 0.54 ± 0.05 (mean ± SEM) in the control group and 0.49 ± 0.04 in the EA group (Figure 3). Electroacupuncture did not affect heart rate, blood pressure (Figure 3), or arrhythmic activity. (Tables 1 and 2).

Figure 3.

Electropuncture and arrhythmias. A, Ischemic risk region (expressed as a fraction of the left ventricle) in control (CN, grey) and electroacupuncture (EA, black) groups. B, Heart rate and mean blood pressure. bpm, beats per minute; BP, blood pressure; occl, occlusion; rep, reperfusion.

Table 1.

Presence of Arrhythmias

	Any Arrhythmia	Any VT	Any SUS VT	Any VF	Any VPBs
CN (n = 5)	5/5	5/5	4/5	2/5	5/5
EA (n = 5)	5/5	5/5	5/5	3/5	5/5
P value	1	1	1	1	1

Abbreviations: CN, control group; EA, electroacupuncture; VT, ventricular tachycardia; SUS VT, sustained ventricular tachycardia (≥10 seconds in duration); VF, ventricular fibrillation; VPBs, ventricular premature beats.

Table 2.

Quantitation of Arrhythmias

	VT Onset, s	# Episodes VT	Duration VT, s	# Episodes SUS VT	Duration SUS VT, s	Duration VF, s	# VPBs
CN (n = 5)
Median	17	28	139	3.0	86	0	49
Mean	14.3	33	142	3.4	89	1.0	48
SEM	3.4	7.2	28.4	1.2	33	0.7	19
EA (n = 5)
Median	9	23	87	4.0	69	2.7	22
Mean	8.2	18	103	3.4	64	7.4	28
SEM	1.2	4.6	19	0.9	15	5.1	15
P value	.17	.14	.47	1.0	.6	.3	.4

Discussion

The primary findings of the current series of experiments were that the Chinese herbal remedies DS and the mixture of DS + JX had no effect on experimental myocardial infarct size in the rat. In addition, in the present model, EA did not reduce infarct size either when it was started 5 minutes prior to coronary occlusion and continued for 5 minutes into reperfusion or 30 minutes before coronary occlusion and maintained for 30 minutes of reperfusion. Electroacupuncture also did not reduce ventricular arrhythmias associated with ischemia/reperfusion.

Herbal Therapies for Myocardial Ischemia/Infarction

Previous studies have suggested that some herbal remedies may have beneficial effects on the cardiovascular system. For example, DS improved survival rate, reduced myocardial infarct size, and reduced ventricular remodeling¹⁶ in rats subjected to a permanent coronary occlusion. In that study, therapy was administered once daily at 0.675 g/kg per d for 1 week prior to coronary occlusion and continued for 2 weeks after surgery. However, the onset of acute myocardial infarction is not predictable, so it is important to determine whether therapy given closer to the time of CAO can acutely reduce infarct size. In our experimental model, which included reperfusion to make it more relevant clinically, and a model in which the therapy was started close to the time of occlusion, neither DS nor the combination of DS + JX demonstrated any benefit. A difference between our negative study and the previously positive one¹⁶ was that the previous study began therapy earlier prior to ischemia.¹⁶ Again, this would be a less relevant model from the clinical perspective of acute myocardial infarction. However, it is feasible that earlier administration of therapy in the settings of unstable angina or accelerating angina might prevent infarction or reduce its extent.

Our findings do not argue against other beneficial effects of DS reported in the literature, such as improvement in flow-mediated vasodilation and carotid intimal thickness, when the agent is administered chronically along with pueraria lobata (gegen) in coronary patients.⁷ Danshen may also be effective in treating angina pectoris.^3,4 Finally, our study also does not rule out the possibility that other herbal remedies, other doses of DS, or DS combined with other herbs might be able to acutely reduce the size of myocardial infarction.^24

–27

Electroacupuncture for Myocardial Ischemia/Infarction

Li et al have shown that EA at the P5-P6 acupoints overlying the median nerve reverse reflex-induced myocardial ischemia by reducing blood pressure.¹³ A reduction of blood pressure and thus myocardial oxygen demand would be expected to lessen ischemia, hence the rationale for studying EA in the setting of acute myocardial infarction. However, in our study, we did not observe a hypertensive response during coronary occlusion nor did we observe a reduction in blood pressure with EA. Our results certainly do not rule out the possibility that patients who have myocardial infarction in the setting of hypertension might benefit from EA. Another possibility is that the use of the anesthetic agents, ketamine and xylazine, in our study blunted any sympathetic response. Despite the results of our study, several other studies have suggested that EA may protect against ischemia/reperfusion injury. Tsou et al showed,¹² in an anesthetized rat model of 30 minutes of coronary occlusion and 10 minutes of reperfusion, that either pretreatment with EA at P6 (stimulation for 30 minutes followed by a 30-minute rest period and subsequent ischemia/reperfusion injury) or starting EA after coronary occlusion had benefits. Rats with 30 minutes of rest between EA preconditioning and coronary occlusion showed a significant decrease in blood pressure, mortality, arrhythmias, and cardiac enzyme leak. Starting EA after ischemia also had benefits of reducing blood pressure, reducing mortality rate, ventricular arrhythmias, and cardiac enzyme leak. At least 2 other reports have suggested that EA reduces ischemia/reperfusion injury in animal models.^11,28 Gao et al ^11,14 showed that in the rat model, the cardioprotective effects of EA were abolished by propranolol, suggesting that β adreno-receptors contribute to mediating the benefits of EA. Lujan et al¹⁵ showed that EA at P5-P6 in conscious rats reduced the incidence of ventricular arrhythmias induced by 3 minutes of proximal coronary occlusion and reperfusion. Of note, this decreased susceptibility to development of ventricular arrhythmias was associated with a reduction in rate pressure product. In contrast to these studies, we did not observe any evidence for a cardioprotective effect of EA on either anatomic myocardial infarct size or arrhythmias, likely because there was no change in heart rate or blood pressure in the EA compared with control groups. Of note is that some previous analyses¹² assessed extent of cardiac injury indirectly (enzyme leak after only a limited period of reperfusion; or ST segment elevation on the ECG), whereas we used the more standard technique of measuring anatomic infarct size utilizing stain with triphenyl tetazolium chloride to identify tissue necrosis and normalizing infarct size by risk zone. In protocol 2A, we utilized 2 controls—one group without any needles (true control) and another with needles placed but without EA. Not all studies have used 2 controls. To our surprise, there was a trend (although not statistically significant) for AN/AR to be higher in the needle only group compared with EA. If we were simply looking at the results in these 2 groups and not taking into account the control group that received no needles, we may have misinterpreted the results as a benefit of EA versus control.

Limitations

There are several potential limitations with our study. We cannot rule out the possibility that anesthesia blunted or masked a beneficial effect of either herbs or EA by altering sympathetic outflow. The EA did not influence heart rate or blood pressure in our study, whereas its beneficial effects in other studies appear to have been related to reductions in these parameters, which would be expected to reduce myocardial oxygen demand and therefore ameliorate ischemia. In protocol 2A, there were several EA rats (n = 6, ∼50%) that fell below the line of regression for AN versus AR (Figure 2C). We cannot rule out the possibility that some of these were responders to EA. Certainly, not all humans or animals are responders to EA. We cannot rule out a type II error, in which a larger number of animals would have resulted in a positive effect. While a formally licensed acupuncturist did not perform the EA procedure, the researcher who did perform it was trained by the Longhurst laboratory at UC Irvine, which has had extensive experience with EA in animal models. A number of studies demonstrate that the influence of EA on cardiovascular function involves central neural processing, mainly through its action on sympathetic activity.^{29

–36} It is possible that any abnormalities in blood gases may minimize the influence of EA on the autonomic neural (especially sympathetic) outflow and hence myocardial oxygen demand. While we did not monitor blood gases, rats were mechanically ventilated, tissues remained pink, and this same model has been used to show that other interventions reduce infarct size. We obtained herbal products of prescription grade from China and used a dose of DS previously shown to reduce infarct size;¹⁶ however, the medicinal potency and clinical efficacy were unknown; it is possible that other doses or preparations of this herb, other combinations, other methods of administration of the herbs, or timing of administration might have worked.^37
–39 It is possible that more chronic use of the herbs as might be used for angina,⁴⁰ would have limited infarct size, but again myocardial infarcts are unpredictable so acute administration of these drugs is a more clinically relevant model.

In our study, drug administration occurred acutely, but prior to coronary occlusion. In our experience, if a drug does not reduce myocardial infarct size, when administered shortly prior to coronary occlusion (when the drug has access to blood flow into the soon-to-be at risk myocardium), it is unlikely for the drug to work if administered shortly after coronary occlusion, when it is harder for the drug to reach the risk zone, since blood flow is cut off. However, our study is also relevant to the situation in which treatment is given before major surgery or elective percutaneous coronary intervention.

In summary, we were neither able to confirm cardioprotective effects of the commonly used herbal remedy DS alone or in combination with JX nor were we able to confirm a benefit of EA on reducing experimental myocardial infarct size or ventricular arrhythmias in the absence of any hemodynamic effect of EA.

Footnotes

Authors’ Note

Dr Jonathan Leor, MD, served as Guest Editor.

Declaration of Conflicting Interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author(s) received no financial support for the research, authorship, and/or publication of this article.

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Absence of Actions of Commonly Used Chinese Herbal Medicines and Electroacupuncture on Myocardial Infarct Size

Abstract

Background:

Methods:

Results:

Conclusion:

Keywords

Introduction

Methods

Protocol 1: Effect of Herbal Medicines on Myocardial Infarct Size

Protocol 2A: Effect of Electroacupuncture on Myocardial Infarct Size

Protocol 2B: Effect of 30 Minutes of Preocclusion Acupuncture on Myocardial Infarct Size

Protocol 3: Effect of Acupuncture and Reperfusion—Induced Arrhythmias in a Non-Necrotic Model

End Points

Statistical Analyses

Results

Protocol 1: Effect of Herbal Medicines on Myocardial Infarct Size

Protocol 2A: Effect of Acupuncture on Myocardial Infarct Size

Protocol 2B: Effect of 30 Minutes of Preocclusion Acupuncture on Myocardial Infarct Size

Protocol 3: Effect of Acupuncture- and Reperfusion-Induced Arrhythmias in a Nonnecrotic Model

Discussion

Herbal Therapies for Myocardial Ischemia/Infarction

Electroacupuncture for Myocardial Ischemia/Infarction

Limitations

Footnotes

Authors’ Note

Declaration of Conflicting Interests

Funding

References