Distinct Activation Patterns of Idioventricular Rhythms and Sympathetically-Induced Ventricular Tachycardias in Dogs with Atrioventricular Block

To investigate mechanisms of ventricular impulse formation in response to sympathetic stimulation in the healthy canine heart in situ, we compared the patterns of ventricular activation during the idioventricular rhythms arising after complete atrioventricular (AV) block and ventricular tachycardias induced by RSG or LSG stimulation. Isochronal maps were generated by computer from 116-127 unipolar electrograms recorded from the entire ventricular epicardium in 15 open chest, anesthetized dogs. In eight of these, bipolar electrograms were recorded with plunge electrodes from 11 selected endocardial sites located below epicardial breakthrough areas. Intracardiac recordings from the His-Purkinje system were made with electrode catheters. After electrograms were recorded during sinus rhythm, complete AV block was induced by injecting formaldehyde into the AV node and idioventricular rhythms occurred spontaneously at a rate of 37 +/- 12 beats/min (mean +/- SD, n = 25). During idioventricular rhythms, endocardial activation preceded the earliest epicardial breakthrough, which occurred in either the right anterior paraseptal region, antero-apical left ventricle, or postero-apical left ventricle. These sites were consistent with a focal origin in the subendocardial His-Purkinje system. Total epicardial activation times lasted for 47 +/- 13 msec (n = 40). Idioventricular rhythms were suppressed by overdrive pacing (intermittent trains of ten beats with decremental cycle length from 500 to 200 msec) or by intravenous calcium infusion (to plasma levels of 10.1-15.2 mM). Right or left stellate ganglion stimulation increased idioventricular rhythm rates (to 52 +/- 13 beats/min, n = 28) and also induced, in all preparations, ventricular tachycardias that had significantly faster rates (189 +/- 55 beats/min, n = 27, P less than 0.005). Ventricular fibrillation was induced after brief runs of ventricular tachycardia in five of the preparations. During ventricular tachycardias, epicardial activation occurred on the right ventricular outflow tract or the postero-lateral wall of the left ventricle, and preceded endocardial activation in 50% of cases. Total epicardial activation times (103 +/- 29 beats/min) were significantly longer than during idioventricular rhythms (P less than 0.005). Ventricular tachycardias displayed overdrive excitation at critical pacing cycle lengths (360-280 msec) and were not suppressed by calcium infusion. Thus, differential mechanisms of impulse formation with distinct localizations can be elicited from healthy ventricular myocardium.     

Effect of Adenosine and Verapamil in Catecholamine-Induced Accelerated Atrioventricular Junctional Rhythm: Insights into the Underlying Mechanism

Accelerated AV junctional rhythm is postulated to he due to enhanced automaticity of a high AV junctional focus. The adenosine response of this rhythm was tested in 17 patients (7 males, 12-83 years). The indications of electrophysiology study were nonspecific palpitation (n = 5), unexplained syncope (n = 6), postablation of accessory pathways (n = 4), and postmodification of AV nodal reentry tachycardia (n = 2). The sinus node and AV nodal functions were normal. Pacing and programmed electrical stimulation failed to induce anv arrhythmia at baseline. The accelerated junctional rhythm (cycle length = 553 ± 134 ms) was initiated spontaneously in all patients after isoproterenol infusion (1-2 μg/min). It was not suppressible bv overdrive pacing. Cessation of isoproterenol infusion terminated the rhythm in all patients. Adenosine (6 mg) reproducibly terminated the accelerated functional rhythm in all patients. In six patients, adenosine suppressed the junctional rhythm without producing AV nodal block. In the other 11 patients, the junctional rhythm was terminated prior to the occurrence of AV nodal block. Verapamil was tested in ten patients and 5 mg of intravenous verapamil terminated the junctional rhythm in all patients. In conclusion, the mechanism of catecholamine-induced accelerated AV junctional rhythm is most likely enhanced automaticity, and catecholamine-induced accelerated AV functional automaticity is sensitive to adenosine and verapamil. Adenosine appears to have differential effects on catecholamine-enhanced AV junctional automaticity and AV nodal conduction. This suggests that, under catecholamine stimulation, adenosine may have different mechanisms of action on AV nodal conduction and automaticity.     

Sinus Rhythm Mapping in a Canine Model of Ventricular Tachycardia

The relationship between electrograms recorded during sinus rhythm and the activation sequence during ventricular tachycardia induced by programmed stimulation was investigated in a canine model of myocardial infarction. Thirteen dogs were studied 3 days (n = 10) or 14 days (n = 3) after coronary occlusion. Sixty-three unipolar electrograms were simultaneously recorded with a sock electrode array connected to a digital recording system, and analyzed by computer. Bipolar electrograms were recorded sequentially from the same sites with an analog recorder. Categories of unipolar electrograms were defined with reference to the QRS complex during sinus rhythm as follows: Class A included electrograms with an intrinsic deflection inscribed within the QRS complex, class B included those which did not exhibit any intrinsic rs deflection, and class C included those with an intrinsic deflection inscribed later than QRS. The epicardial distribution of each class of electrograms was significantly different between the preparations with, and those without inducible tachycardia (72% versus 63% of electrograms being in class A, 20% versus 35% in class B, and 8% versus 2% in class C; p less than 0.005). When tachycardia was inducible, class C epicardial electrograms were located in an area extending across the region of infarction, which corresponded to the common reentrant pathway of figure-of-eight patterns mapped during tachycardia. When ventricular tachycardia was not inducible, class B electrograms were recorded all over this region. The morphology of bipolar electrograms had no predictive value in identifying the common reentrant pathway. These results support the view that the inducibility of reentrant tachycardia is dependent upon critically located delayed activity detected during sinus rhythm by unipolar recordings.     

A 21st Century Problem: Cannabis Toxicity in a 13-Month-Old Child

Background

Cannabis is one of the most abused drugs worldwide, with more than 20 million users in the United States (US). As access to cannabis products increases with expanding US legislation and decriminalization of marijuana, emergency physicians must be adept in recognizing unintentional cannabis toxicity in young children, which can range from altered mental status to encephalopathy and coma.

Altered Mental Status as the Primary Presentation of Intussusception in a 3-Month-Old Child Diagnosed by Point-Of-Care Ultrasonography

BackgroundIntussusception can lead to significant morbidity in affected children secondary to tissue ischemia and necrosis. When a child outside of the classic age range presents with symptoms other than intermittent abdominal pain, the diagnosis of intussusception can be difficult and is often delayed.Case ReportWe present the case of a three-month-old boy who presented to the emergency department with waxing and waning mental status and seizure-like activity who was ultimately diagnosed with intussusception. The effective use of bedside ultrasonography, by the attending pediatric radiologist, enabled an interdisciplinary team to explore abdominal etiologies in parallel with testing for more commonly seen causes of altered mental status. This led to an expedited diagnosis and successful definitive management.Why Should an Emergency Physician Be Aware of This?Intussusception is a common pediatric emergency encountered by emergency physicians where a timely diagnosis can have a profound impact on patient outcomes. Previous case reports highlight how easily intussusception can be overlooked with this atypical neurologic presentation. Furthermore, because patients with profound altered mental status are often too ill to leave the emergency department for diagnostic testing, bedside abdominal ultrasonography may be helpful in these patients.     

Emergency Medicine Resident Rotation in Pediatric Emergency Medicine: What Kind of Experience Are We Providing?

OBJECTIVES: To characterize emergency medicine (EM) residents' clinical experience during a pediatric emergency medicine (PEM) rotation. METHODS: Prospective observational study of EM resident-patient encounters in a children's hospital emergency department (ED). RESULTS: Fifty-six residents participated in the study. The mean (+/-SD) patient age was 6.3 (+/-5.6) years. Ambulatory infectious disease, respiratory illness, and wound management represented almost 50% of final diagnoses. Six and a half procedures/resident were performed per rotation, mainly nonemergent procedures, whereas resuscitations and child abuse evaluations were rare. A minority of patients required data interpretation: 34.4% had laboratory testing, 24.6% had radiographic studies, and 2.3% had electrocardiograms. CONCLUSIONS: Analysis of patient encounters during a PEM rotation showed deficiencies in critical care procedures, resuscitations, child abuse evaluations, and neonatal evaluations. Quantitative data of skills utilized during rotations can be used by residency programs to identify and correct deficiencies in their residents' PEM education.     

Atopic Keratoconjunctivitis: A Pediatric Case Report

Ophthalmologic complaints can be challenging to diagnose. Atopic keratoconjunctivitis is a chronic, noninfectious, allergic eye condition not commonly seen in children and often confused with other eye disorders. Early diagnosis and treatment can control patient symptoms and prevent further complications. Left untreated, atopic keratoconjunctivitis can lead to corneal scarring and vision loss if not treated properly. This case report focuses on a pediatric patient who presented with persistent and worsening eye irritation despite multiple office visits and treatment.     

Hemorrhagic Pericardial Cyst Diagnosis Accelerated by Emergency Physician Echocardiography: A Case Report

Background

The differential diagnosis for chest pain in the emergency department is broad and includes both benign and life-threatening conditions–with pericardial cyst as a rare example. Emergency physician-performed point-of-care focused cardiac ultrasound (FOCUS) is increasingly recognized as a useful modality in the evaluation of patients with chest pain.

Ultrasound Findings in Tension Pneumothorax: A Case Report

Background

Delayed recognition of tension pneumothorax can lead to a mortality of 31% to 91%. However, the classic physical examination findings of tracheal deviation and distended neck veins are poorly sensitive in the diagnosis of tension pneumothorax. Point-of-care ultrasound is accurate in identifying the presence of pneumothorax, but sonographic findings of tension pneumothorax are less well described.

Acute Gastric Volvulus in a Six-Year-Old: A Case Report and Review of the Literature

Background

First described in the pediatric population in 1899 by Oltmann, pediatric gastric volvulus is a rare disease, but carries a high mortality rate. Due to vague signs and symptoms it can easily be mistaken for gastroenteritis or appendicitis, but unique radiographic findings can help illuminate the diagnosis. The pathophysiology of gastric volvulus is related to an abnormality in the attachment of at least one of the gastric ligaments, which can occur either primarily or secondarily. The abnormality in these ligaments allows the stomach to freely rotate, eventually causing an obstruction. We describe a unique case occurring in a 6-year-old with no pre-exiting medical conditions as well as the associated radiographic images.

Objectives

Our aim is to discuss the presentation and management of a potentially lethal intra-abdominal process that mimics far more benign disease entities and to highlight the pertinent radiographic findings.

Case Report

A previously healthy 6-year-old female presented to the emergency department in the middle of the night after sudden onset of vomiting and abdominal pain. On exam her heart rate was mildly elevated but all other vital signs were within normal limits. She was assessed with an abdominal x-ray and given ondansetron. After settling with her parents and having no further bouts of emesis she was sent home. She returned that afternoon febrile with increasing abdominal pain and emesis. Abdominal x-ray revealed a massively distended stomach and left diaphragmatic eventration. She underwent operative intervention and improved over the course of the following week.

Conclusion

Acute gastric volvulus presents a diagnostic challenge. In patients with vague abdominal complaints knowledge of the typical x-ray findings is essential in early identification and treatment.     

ST-Elevation Myocardial Infarction in the Presence of Biventricular Paced Rhythm

Background

In the diagnosis of acute myocardial infarction (AMI), the presence of baseline left bundle branch block or a permanent pacemaker rhythm poses a challenge.

Objective

We present a case report highlighting this challenge, along with a review of pertinent literature.

Case Report

A 70-year-old female with known severe idiopathic dilated cardiomyopathy and moderate coronary artery disease who was status post−biventricular pacemaker/implantable cardioverter defibrillator insertion was brought to our institution via Emergency Medical Services with recurrent firing of her implantable cardioverter defibrillator and syncope. After stabilization in the Emergency Department and treatment with intravenous amiodarone, the patient admitted to having ongoing chest pains. The electrocardiogram revealed evidence of biventricular pacing with superimposed ST-segment elevations in the anterolateral leads indicative of myocardial injury. She underwent prompt angiography, thrombectomy, and bare-metal stent insertion to a totally occluded proximal left anterior descending coronary artery, with resolution of her chest pain and improvement in the ST-segment changes.

Conclusions

Despite proposed criteria that aid in the recognition of AMI with underlying left bundle branch block and paced rhythm; the advent of new pacing modalities and the potential variability of pacing sites impose additional diagnostic challenges requiring higher level of suspicion and better physician awareness.     

The Rhythm of Relating in a Paradigm of Wholeness

The importance of relating to the rhythm of another person's interactive pattern is integral to helping people move through illness and disruptive events. At times of chaos, a person's rhythm may be irregular and difficult to sense, but transformation to higher levels of organization often occurs at far-from-equilibrium states. Nurses should develop a tolerance for ambiguity and uncertainty and ang in there with clients until a new rhythm emerges.     

Accelerated Junctional Tachycardia at a Rate of 190 Beats/Minute Following Cryosurgery and Aneurysmectomy for Ventricular Tachycardia: A Case Report

In this case study we report a 59-year-old man who underwent combined aneurysectomy, endocardial resection, and cryosurgery for recurrent ventricular tachycardia. Following surgery he developed an accelerated junclional tachycardia with rates up to 190/min arising near the area of cryoablation which involved the junctional region. Using intracavitary recording and stimulation this tachycardia was shown to arise from ihe junctional area and had characteristics suggesting accelerated automaticity. During the electrophysiological study the focus of the tachycardia was temporarily obtunded by catheter trauma. After reappearance of the arrhythmia, successful suppression was achieved using diphenylhydantoin. (PACE, Vol. 5, May-June, 1982)     

Comparison Between Patients with and without Reliahle Ventricular Escape Rhythm in the Presence of Long Standing Complete Atrioventricular Block

The underlying heart rhythm was evaluated in 74 patients with complete atrioventricular block and had a permanent pacemaker implantation. The pacing was inhibited for 10 seconds or until the patient developed symptoms of presyncope or syncope. Fifty-six patients (74%) had a reliable escape with a mean cycle length of 2010 ± 596 msec and a mean escape interval of 2335 ± 971 msec. In 93% of these piatients the escape interval was < 4 seconds. The patients without reliable escape (24%), developed symptoms only after a mean of 7153 ± 1875 msec. The duration of the conduction disorder was longer in the patients without escape and the intraventricular conduction was slower. More patients without escape were treated with antiarrhythmic agents. Forty-eight patients were followed for 1 year and underwent at least two different studies and 13% had different results at different tests. In conclusion, patients without reliable escape have a longer history of conduction disorder, a slower intraventricular conduction, and are frequently treated with antiarrhythmic agents. Even patients with reliable escape occasionally may show a greater pacemaker dependence; therefore, they should also be considered as pacemaker dependent.     

Bilateral Retinal Detachment in a Pediatric Patient

Background

Pediatric retinal detachments occur rarely, and thus may be easily missed. Without treatment, this condition leads to permanent vision loss. Patients with Stickler syndrome, an inherited disorder of collagen synthesis, are more likely to have retinal detachments than the general population.