Electromechanical dissociation: diagnosis, pathophysiology, and management

Clinical and Angiographic Features of Patients With Out-of-Hospital Cardiac Arrest and Acute Myocardial Infarction

BACKGROUND

Sudden cardiac arrest is a serious complication of acute myocardial infarction (MI). Although in-hospital mortality from MI has decreased, the mortality of MI patients complicated with out-of-hospital cardiac arrest (OHCA) remains high. However, the features of acute MI patients with OHCA have not been well known.

OBJECTIVES

We sought to characterize the clinical and angiographic features of acute MI patients with OHCA comparing with those without OHCA.

METHODS

We retrospectively analyzed 480 consecutive patients with acute MI undergoing percutaneous coronary intervention. Patients complicated with OHCA were compared with patients without OHCA.

RESULTS

Of the patients, 141 (29%) were complicated with OHCA. Multivariate analysis revealed that age (odds ratio [OR]: 0.8; 95% confidence interval [CI]: 0.7 to 0.9 per 5 years; p < 0.001), estimated glomerular filtration rate (OR: 0.8; 95% CI: 0.7 to 0.8 per 10 ml/min/1.73 m²; p < 0.001), peak creatine kinase-myocardial band (OR: 1.3; 95% CI: 1.2 to 1.4 per 10² U/l; p < 0.001), calcium-channel antagonists use (OR: 0.4; 95% CI: 0.2 to 0.7; p = 0.002), the culprit lesion at the left main coronary artery (OR: 5.3; 95% CI: 1.9 to 15.1; p = 0.002), and the presence of chronic total occlusion (OR: 2.9; 95% CI: 1.5 to 5.7; p = 0.001) were significantly associated with OHCA.

CONCLUSIONS

Younger age, no use of calcium-channel antagonists, worse renal function, larger infarct size, culprit lesion in the left main coronary artery, and having chronic total occlusion were associated with OHCA.

Relation of Chronic Total Occlusion to In-Hospital Mortality in the Patients With Sudden Cardiac Arrest Due to Acute Coronary Syndrome

Although the presence of chronic total occlusion (CTO) has been associated with long-term mortality in the patients with ST-segment elevation myocardial infarction, the influence of having CTO on in-hospital mortality in sudden cardiac arrest (SCA)-acute coronary syndrome (ACS) patients has not been reported. Therefore, we examined the association between the presence of CTO and in-hospital mortality in those patients. Consecutive 106 SCA-ACS patients who received coronary angiography were retrospectively included. The factors associated with in-hospital mortality were analyzed. Among 106 patients, 40 (38%) patients died during hospitalization. Multivariate analysis revealed presence of CTO dependent on infarct-related artery (IRA-dependent-CTO) (hazard ratio [HR] = 2.88, p = 0.004), diabetes mellitus (HR = 2.04, p = 0.044), percutaneous cardiopulmonary support use (HR = 2.22, p = 0.045), successful recanalization (HR = 0.31, p = 0.004), and peak creatine kinase muscle-brain fraction (HR = 1.11, p < 0.001) were significantly associated with mortality. In conclusion, presence of IRA-dependent-CTO was significantly associated with in-hospital mortality in SCA-ACS patients.

Tissue Plasminogen Activator Use in Cardiac Arrest Secondary to Fulminant Pulmonary Embolism

Background

Tissue plasminogen activator (tPA) is used emergently to dissolve thrombi in the treatment of fulminant pulmonary embolism. Currently, there is a relative contraindication to tPA in the setting of traumatic or prolonged cardiopulmonary resuscitation > 10 minutes because of the risk of massive hemorrhage.

Methods

Our single-center, retrospective study investigated patients experiencing cardiac arrest (CA) secondary to pulmonary embolus. We compared the effectiveness of advanced cardiac life support with the administration of tPA vs. the standard of care consisting of advanced cardiac life support without thrombolysis. The primary endpoint was survival to discharge. Secondary endpoints were return of spontaneous circulation (ROSC), major bleeding, and minor bleeding.

Results

We analyzed 42 patients, of whom 19 received tPA during CA. Patients who received tPA were not associated with a statistically significant increase in survival to discharge (10.5% vs. 8.7%, P = 1.00) or ROSC (47.4% vs. 47.8%, P = 0.98) compared to the control group. We observed no statistically significant difference between the groups in major bleeding events (5.3% in the tPA group vs. 4.3% in the control group, P = 1.00) and minor bleeding events (10.5% in the tPA group vs. 0.0% in the control group, P = 0.11).

Conclusion

This study did not find a statistically significant difference in survival to discharge or in ROSC in patients treated with tPA during CA compared to patients treated with standard therapy. However, because no significant difference was found in major or minor bleeding, we suggest that the potential therapeutic benefits of this medication should not be limited by the potential for massive hemorrhage. Larger prospective studies are warranted to define the efficacy and safety profile of thrombolytic use in this population.

Electrical therapy for post defibrillatory pulseless electrical activity

BACKGROUND

Defibrillation may convert ventricular fibrillation (VF) only to reveal profound mechanical dysfunction. Survival following this dysfunction, known as pulseless electrical activity (PEA) and electromechanical dissociation (EMD), is uncommon. We sought to evaluate an electrical therapy for primary post shock PEA following short duration VF.

METHODS AND RESULTS

Forty-eight episodes of VF, lasting 110 +/- 25 s, were induced in 16 anesthetized dogs. Following defibrillation, 35 episodes met PEA criteria (ABP < or = 36 mmHg diastolic and pulse pressure < or = 14 mmHg in the first 20 s post shock). These post defibrillation PEA episodes were either Not Treated (NT) or Treated (T) with packets of 4-20 monophasic 0.2 ms 50-100 Hz pulses of 20-60 V applied across the tip and coil of an integrated bipolar transvenous defibrillation lead positioned in the right ventricle. The therapeutic endpoint was return of spontaneous circulation (ROSC; self-sustained ABP > or = 60 mmHg diastolic and/or > or = 100 mmHg systolic) for over 2 min. In the Not Treated group, only 4 of 19 (21%) episodes spontaneously recovered to ROSC in 123 +/- 49 s while in the Treated group, 11 of 16 (69%) of the PEA episodes achieved ROSC in 102 +/- 92 s.

CONCLUSIONS

Electrical therapy increased the likelihood of ROSC in primary post defibrillation PEA three-fold (P < 0.01). Recovery occurred in the absence of thoracic compression, mechanical ventilation, or adjunctive drug therapy.

Thrombolysis during cardiopulmonary resuscitation in fulminant pulmonary embolism: a review

OBJECTIVE

To review current knowledge on thrombolysis in patients with fulminant pulmonary embolism (FPE) who need cardiopulmonary resuscitation (CPR).

DATA SOURCES

The bibliography for the study was compiled through a search of different databases between 1966 and 2000. References cited in the articles selected were also reviewed.

STUDY SELECTION

The selection criteria included all reports published on thrombolysis, pulmonary embolism, and CPR, from case reports and case series to controlled studies.

DATA SYNTHESIS

Very few studies evaluated thrombolysis in cases of FPE that required CPR and most of these were clinical case reports and case series with a low level of scientific evidence. There has been no clinical trial to address this issue.

CONCLUSIONS

FPE can frequently produce cardiac arrest, which has an extremely high mortality despite application of the usual CPR measures. The administration of thrombolytic therapy during CPR could help to reduce the mortality, although it has classically been contraindicated. There are no published clinical trials or other high-grade studies that evaluated the efficacy and safety of this approach. From the few existing studies, it can be inferred that thrombolysis may be efficacious and safe for patients with FPE who need CPR. However, a clinical trial is required to provide evidence of value for sound clinical decision-making.

Factors affecting short- and long-term prognosis among 1069 patients with out-of-hospital cardiac arrest and pulseless electrical activity

AIMS

To describe the epidemiology, resuscitation factors and prognosis among a consecutive population of patients suffering from out-of-hospital cardiac arrest (OHCA) where pulseless electrical activity (PEA) was the first arrhythmia recorded on emergency medical services (EMS) arrival.

METHODS

Analysis of data collected prospectively on all patients regardless of age succumbing to OHCA during 1980-1997 in the community of Gothenburg where EMS initiated resuscitative measures.

RESULTS

4662 patients with OHCA were attended by the EMS during the study period. Of these, 1069 (23%) were judged as having PEA as the first recorded arrhythmia; 158 (15%) of these were admitted alive to hospital and 26 (2.4%) were discharged alive. Survivors to discharge had a significantly larger share of bystander cardiopulmonary resuscitation (CPR) (28 vs. 8%, P=0.008), significantly higher levels of consciousness (8% awake vs. 0%, P<0.001) and higher median systolic blood pressure (145 vs. 106 mmHg, P<0.001) on arrival at hospital. No patient with unwitnessed cardiac arrest and PEA over 80 years old survived.

CONCLUSION

Survival among patients suffering from OHCA and PEA is poor, especially among the elderly unwitnessed cases and those who do not receive bystander CPR. The latter seems to be of utmost importance among these patients.

Accuracy and impact of presumed cause in patients with cardiac arrest

BACKGROUND

International guidelines recommend differentiation between cardiac and noncardiac causes of cardiac arrest. The aim of this study was to find the rate of agreement between primarily postulated and definitive causes of cardiac arrest.

METHODS AND RESULTS

We retrospectively analyzed the primarily presumed cause of cardiac arrest as determined by the emergency room physician on admission in all patients admitted to the emergency department of one urban tertiary care hospital. This was compared with the definitive cause as established by clinical evidence or autopsy. Within 4 years, the initially presumed cause was unclear in 24 (4%) of 593 patients. In the remaining 569 patients, the presumed cause was correct in 509 (89%) and wrong in 60 (11%) cases. Cardiac origin was presumed in 421 (71%) and the definitive cause in 408 (69%) cases. Noncardiac origin was presumed in 148 (25%) and the definitive cause in 185 (31%) patients. Presumed cardiac cause was sensitive (96%) but less specific (77%). Noncardiac causes such as pulmonary embolism, cerebral disorders, or exsanguination were those most frequently overlooked. Asystole occurred significantly more often in patients in whom presumed cause remained undetermined or differed from the definitive cause.

CONCLUSIONS

Cause of cardiac arrest is not as easily recognized as anticipated, especially when the initial rhythm is different from ventricular fibrillation. This might affect comparability of study results, therapeutic strategies, prognosis, and outcome. Patients in whom the presumed cause was confirmed as being correct had significantly better survival and neurological outcome.

Adrenaline-responsive electromechanical dissociation

Electromechanical dissociation (EMD) occurs when there is no detectable blood pressure in the presence of organised electrocardiographic activity. This condition excludes pulseless ventricular tachycardia, and traditionally was thought to result from a failure of electrical depolarisation in the myocardium to elicit mechanical contraction. It is now understood from echocardiographic evidence that 'pseudo-EMD' is more common-where electrical activity is associated with myocardial contractions too weak to sustain a detectable blood pressure [1]. Three cases of EMD in association with subarachnoid haemorrhage (SAH) are described. This form of cardiovascular collapse appears to respond readily to the use of adrenaline. To our knowledge, this has not been reported previously. We suggest that this form of EMD occurs despite adequate myocardial function and results from sympathetic failure with loss of peripheral vascular resistance.

Use of cardiopulmonary bypass, high-dose epinephrine, and standard-dose epinephrine in resuscitation from post-countershock electromechanical dissociation

STUDY OBJECTIVE

To determine the effects of cardiopulmonary bypass with standard-dose epinephrine, high-dose epinephrine, and standard-dose epinephrine on perfusion pressures, myocardial blood flow, and resuscitation from post-countershock electromechanical dissociation.

DESIGN

Prospective, controlled laboratory investigation using a canine cardiac arrest model randomized to receive one of three resuscitation therapies.

INTERVENTIONS

After the production of post-countershock electromechanical dissociation, 25 animals received ten minutes of basic CPR and were randomized to receive cardiopulmonary bypass with standard-dose epinephrine, high-dose epinephrine, or standard-dose epinephrine.

MEASUREMENTS AND MAIN RESULTS

Myocardial blood flow was measured using a colored microsphere technique at baseline, during basic CPR, and after intervention. Immediate and two-hour resuscitation rates were determined for each group. Return of spontaneous circulation was achieved in eight of eight cardiopulmonary bypass with standard-dose epinephrine compared with four of eight high-dose epinephrine and three of eight standard-dose epinephrine animals (P less than .04). One animal was resuscitated with CPR alone and was excluded. Survival to two hours was achieved in five of eight cardiopulmonary bypass with standard-dose epinephrine, four of eight high-dose epinephrine, and three of eight standard-dose epinephrine animals (NS). Coronary perfusion pressure increased significantly in the cardiopulmonary bypass with standard-dose epinephrine group when compared with the other groups (cardiopulmonary bypass with standard-dose epinephrine, 76 +/- 45 mm Hg; high-dose epinephrine, 24 +/- 12 mm Hg; standard-dose epinephrine, 3 +/- 14 mm Hg; P less than .005). Myocardial blood flow was higher in cardiopulmonary bypass with standard-dose epinephrine and high-dose epinephrine animals compared with standard-dose epinephrine animals but did not reach statistical significance. Cardiac output increased during cardiopulmonary bypass with standard-dose epinephrine (P = .001) and standard-dose epinephrine (NS) compared with basic CPR but decreased after epinephrine administration in the high-dose epinephrine group (NS).

CONCLUSION

Resuscitation from electromechanical dissociation was improved with cardiopulmonary bypass and epinephrine compared with high-dose epinephrine or standard-dose epinephrine alone. However, there was no difference in survival between groups. Cardiopulmonary bypass with standard-dose epinephrine resulted in higher cardiac output, coronary perfusion pressure, and a trend toward higher myocardial blood flow. A short period of cardiopulmonary bypass with epinephrine after prolonged post-countershock electromechanical dissociation cardiac arrest can re-establish sufficient circulation to effect successful early resuscitation.

The case against intraoperative ECG monitoring

It can be seen that ECG monitoring has its limitations; however, if it is employed correctly, it can be an invaluable adjunct to physical monitoring. The ECG does not provide information about the cardiac contractile state or hemodynamic status and may not always permit the facile resolution of dysrhythmias; however, in conjunction with other forms of cardiovascular monitoring, the ECG permits the anesthetist to have greater confidence in cardiovascular events occurring during anesthesia and permits the early detection and treatment of cardiac rhythm disturbances.

Electromechanical dissociation. Treatable causes of a dire cardiac emergency

Electromechanical dissociation (EMD) may be primary, due to disease of the heart muscle itself, or secondary to alterations in loading conditions of the heart. Factors such as internal hemorrhage, acute cardiac tamponade, tension pneumothorax, acute pulmonary embolism, and inflow or outflow obstructions of the heart may be responsible for changes in loading. Myocardial ischemia, myocardial depressant overdose, and other conditions may also contribute to secondary EMD. If detected early, these secondary forms of EMD may respond to treatment. Drugs for resuscitation of a patient with EMD include epinephrine, atropine sulfate, and, in selected instances, calcium.

Correction of metabolic acidosis in experimental CPR: a comparative study of sodium bicarbonate, carbicarb, and dextrose

STUDY OBJECTIVE

Carbicarb, sodium bicarbonate, and 5% dextrose were compared for effects on resuscitability in a canine model of electromechanical dissociation after ventricular fibrillation.

DESIGN/INTERVENTIONS

21 healthy mongrel dogs were anesthetized with pentobarbital, intubated, and mechanically supported. They were instrumented to measure heart rate, arterial pressure, pulmonary artery pressure, right atrial pressure, cardiac output, and arterial and mixed venous blood gases. The dogs were then subjected to a protocol that consisted of three successive CPR episodes. During each episode they were treated with repeated injections of one of the three substances, randomly chosen. After two minutes of ventricular fibrillation and four minutes of electromechanical dissociation, CPR was started with a thumper (rate, 60; duty cycle, 50%). If recovery was not obtained after five minutes of CPR, 1 mEq/kg carbicarb or sodium bicarbonate or 5 mL D5W was injected in the right atrium. Half the dose of the same substance was injected every five minutes thereafter; 1 mg epinephrine was also injected every five minutes until recovery. Hemodynamic and gasometric evaluations were performed five and 20 minutes after recovery. This later evaluation served as baseline for the next CPR episode.

MEASUREMENTS AND MAIN RESULTS

The duration and success rates of CPR are similar in the three CPR groups. Hemodynamic parameters were also similar during recovery. Bicarbicarb and sodium bicarbonate increased bicarbonate levels and corrected pH in the arterial and mixed venous blood. There was no difference in the blood gas values after carbicarb and sodium bicarbonate.

CONCLUSION

In this model of cardiac arrest, carbicarb was not superior to sodium bicarbonate in the correction of metabolic acidosis during CPR.