Stress-Specific Influences of Opioids on Cardiac Electrical Stability

Opioids and Arrhythmias. Evidence is provided indicating that the action of opioids on cardiac electrical stability is contingent on the nature of the stress that impinges on the myocardium. This concept is illustrated by the studies of three clinically relevant conditions, namely, acute behavioral stress, hemorrhage, and myocardial ischemia. During aversive conditioning in dogs, morphine sulfate has been found to prevent the stress-induced reduction in cardiac electrical stability. This protective effect is significantly blunted by administration of atropine, indicating that enhanced vagal activity plays a major role. However, there is a remaining component of morphine's action, which is probably due to reduced perception of the aversive stress. In the context of hemorrhage, the mu-selective agonist fentanyl substantially reduces the profibrillatory effect of this physiological stress. The main mechanism involved in this condition is amplification of baroreceptor sensitivity leading to inhibition of cardiac sympathetic drive. Full activation of mu receptors with fentanyl is also effective in reducing vulnerability to fibrillation during acute coronary artery occlusion. This effect was due to vagal efferent activation and not to enhanced baroreceptor responsiveness as in the case of hemorrhage. Administration of the partial mu-agonist buprenorphine does not exert an antifibrillatory action. Collectively, these results not only demonstrate the potent stabilizing influence of opioids on cardiac rhythm but also the stress specificity of the intermediary mechanisms.     

Phosphine gas poisoning

Phostoxin is a fumigant used in rural areas. We report a case of phostoxin ingestion which resulted in the release of lethal phosphine gas. The patient developed a profound metabolic acidosis and cardiovascular depression and died. During treatment and after death, he continued to emit the noxious gas which was dangerous to staff, and resulted in evacuation of the emergency department. Such events tend to be associated with myth and hysteria and the lack of ready access to reliable information. They represent a unique challenge to the emergency physician.     

Reliability of an Automatic Sensing Test with Beat-to-Beat Display of the Signal Amplitude

In contrast to testing of the capture threshold, the reliability of sensing tests has been little studied. This study was performed to test the automatic sensing algorithm included in the Biotronik pacing systems. The automatic measurements made by the devices were compared with the direct manual measurements made of 271 atrial (72%) or ventricular (28%) electrograms recorded in ten patients. A high correlation(r = 0.995, P < 0.0001) was found between the two types of measurements. The use of this function should facilitate the verification of accurate sensing during the long-term follow-up of pacemaker patients, and offers a tool to analyze the variations in amplitude of intracardiac signals.     

External Non-invasive Cardiac Pacing: A Comparative Hemodynamic Study of Two Techniques with Conventional Endocardial Pacing

Out-of-hospital therapy for cardiac arrest due to bradyarrhythmias or asystole is pharmacologic and the outcome is uniformly dismal. Optimal therapy for the latter disturbances may be artificial cardiac pacing, but conventional invasive pacing techniques are not employed or are of limited value in the out-of-hospital and emergency department setting. This investigation compared the hemodynamic effects of two techniques of non-invasive external pacing: 1) transcutaneous transthoracic pacing (TTP) and 2) tongue-to-epigastrium pacing (TEP), with conventional transvenous right ventricular endocardial pacing (RVEP) in a closed-chest, chronic heart block canine model. All techniques significantly increased (p less than .001) cardiac output (CO). However, CO and mean arterial pressure (MAP) measured during external pacing with either non-invasive technique were significantly greater than that during RVEP (p less than .001). TEP produced vigorous skeletal muscle stimulation and, in the canine model, it produced contraction resulting in impaired ventilation, hypoxemia, and a decrease in systemic vascular resistance. TTP in this model resulted in improved MAP and CO when compared with control and RVEP values and did not affect arterial or mixed venous blood gas values. Thus, this study demonstrates that noninvasive TTP is comparable to RVEP in its hemodynamic effects. TTP may offer definitive non-invasive therapy for a subset of victims of out-of-hospital cardiac arrest.     

Diagnosis of Ventricular Tachycardia Using a Pacemaker Holter Function

The diagnosis of ventricular tachycardia (VT) using the Holter function of an implanted pacemaker has not yet been reported. We present the case of a patient with episodes of slow VT. hemodynamically stable, but in whom long lasting attacks were not identified by the patient as VT recurrences, finally leading to progressive heart failure. Prospective analysis of the 24-hour ECG and comparison with the pacemaker Holter data allowed us to determine diagnostic criteria to recognize VT using the pacemaker Holter function. Using these criteria it was possible to retrospectively diagnose VT occurrence during the weeks when the patient was out-of-hospital.     

The Role of Animal Models in Electrophysiologic Studies of Life-Threatening Arrhythmias

Animal models have made substantial contributions to the understanding of basic electrophysiologic principies and arrhythmia mechanisms, as well as to the deveJopment of antiarrhythmic drugs, devices and procedures. The field of clinical electrophysiology has progressed very dramatically and there have also been advances in the basic laboratory that bear relevance In the methods, design and inferpretafion of clinical electrophysioiogic testing, and to the application of new, potential antiarrhythmic interventions.     

Defining Patients at High Risk for Gastrointestinal Hemorrhage after Drug‐Eluting Stent Placement: A Cost Utility Analysis

Introduction: The study goal was to evaluate the cost‐effectiveness of drug‐eluting stent (DES) placement with consideration of gastrointestinal (GI) bleeding risk. DES reduce the need for future coronary revascularization, but require prolonged dual anti‐platelet (DAT) therapy, which may increase the risk for GI bleeding. While DES have been found to be cost‐effective in patients at average risk for GI bleeding, they may not be the most cost‐effective strategy in higher risk patients. Methods: A Markov model was created to compare DES with bare metal stents (BMS). Patients were a hypothetical cohort of 60‐year‐old individuals with coronary artery stenosis that required nonemergent percutaneous coronary revascularization (PCI). The primary outcomes were the threshold incremental risks of GI bleeding from DAT based on willingness to pay (WTP) of $50,000, $100,000, and $150,000 per quality adjusted life year (QALY) gained. Results: For a WTP of $100,000, the relative risk of GI bleeding from DAT could be as high as 10.8 (when compared to aspirin alone) before DES would no longer be cost‐effective. In patients with two risk factors for GI bleeding, the threshold relative risk could be as low as 1.6. Conclusion: In average‐risk patients, the risk of GI bleeding from DAT can be substantial without affecting the cost‐effectiveness of DES. However, DES are unlikely to be cost‐effective in patients with two or more risk factors for GI bleeding. (J Interven Cardiol 2010;23:179‐187)     

Cutaneous Alternariosis in an Adolescent Patient

Abstract:  Cutaneous alternariosis is a rare infection typically observed only in immunocompromised adults, but we report here that the infection can occur in apparently healthy adolescents. We saw a clinically healthy adolescent boy who presented with cutaneous alternariosis 6 weeks after suffering a laceration to his right ankle. Treatment with itraconazole resulted in significant improvement after 1 month.     

Late Retesting of System Performance in ICD Patients Without Spontaneous Shocks

One hundred five implantable cardioverter defibrillator (ICD) patients (71 ± 9 years of age, 83% men) without spontaneous ICD discharges for ≥ 12 months were tested to assess high voltage (HV) circuit integrity and the system's ability to recognize and terminate ventricular fibrillation (VF). Indications for ICD implantation were sustained ventricular tachycardia (VT) (35%), cardiac arrest (27%), and inducible VT (38%). Eighty-two percent of the patients had coronary artery disease (CAD), and the mean left ventricular ejection fraction (LVEF) was 36%± 13%. Results: One hundred patients had inducible VF and five did not. Testing led to ICD reprogramming in 50 (49%) patients. Two (1.9%) patients required ICD replacement: (1) a 45-year-old patient with a Ventritex 110 ICD implanted for 13 months interfaced with a CPI 0062 lead implanted for 46 months could not be defibrillated internally (impedance nonmeasurable); (2) an 82-year-old patient with a 23-month-old Medtronic 7219 ICD interfaced with 6936 and 6933 leads whose defibrillation threshold (DFT) had doubled since implantation (24 J from 12 J). Lead fractures were found in both cases (proximal coil of the 0062, and subcutaneously in the 6933). Based on DFT determinations, the first shock output was programmed lower in 37 patients and higher in 10 patients. Shock pulse width was changed in one patient and the ventricular refractory period in another. No programming changes were made in 54 (51%) patients. Conclusions: (1) Late testing of HV circuit integrity in ICD patients without an ICD shock in ≥ 12 months identifies previously unsuspected HV lead fractures; (2) chronic DFT testing resulted in HV output reprogramming in one-half of the patients.