Termination of ventricular tachycardia by carotid sinus massage

A Legal and Forensic Medicine Approach to Police Physical Intervention Techniques in High-Risk Situations

Background: The physical intervention techniques (PITs) typically used by the police in troublesome situations are examined in terms of injuring potential depending on whether they target a body zone of high, medium or low vulnerability. Based on legal and forensic considerations, and principles of congruence, opportunity and proportionality, a need exists to favor opponent locking and arrest techniques targeting non-vulnerable zones to minimize the risk of severe damage. Methods: A search of the training manuals for the different kind of law of enforcement officers was carried out. Revision of injuries was available from electronic databases of academic o medical journals. Results: Three different locking and arrest PITs based on operational tactical procedures (OTP) that avoid zones of high or medium vulnerability are proposed. The new techniques use blocking, diverting and grabbing of the upper and lower limbs, followed by dislocation and locking of the same targets. Conclusions: The damaging potential of such PITs was assessed in terms of anatomical region and most were found to have a high risk of severe damage. The alternative PITs proposed here, which rely on OTP, improve in legal and forensic medical terms on existing choices and dramatically reduce the risk of injuring arrestees.

Cardioinhibitory reflex due to a karate kick: a case report

This article describes the case of a 17-year-old adolescent boy who received a foot kick in the trunk area from an expert in karate. He presented with immediate cardiocirculatory arrest. After a prolonged resuscitation, he was transferred to a hospital where he died 5 days later without ever regaining consciousness. Postmortem investigations including autopsy, radiology, histology, toxicology, and postmortem chemistry were performed that showed signs of multiple organ failure, an acute hemorrhage in the region of the celiac plexus, and signs of medical resuscitation. No preexisting disease, particularly those concerning the heart, was objectified. The cause of death was attributed to multiple organ failure after a prolonged cardiocirculatory arrest. Concerning the origin of the cardiac arrest, 2 hypotheses were considered-a cardioinhibitory reflex and a cardiac contusion (commotio cordis). Because of the presence of traumatic lesions in the celiac plexus, the first hypothesis was finally submitted. This case is reported because rare cases of sudden death from celiac reflex are described in the literature where it is almost impossible to find references with accurate documentation. The presented case confirms the importance of detailed documentation of the circumstances and postmortem investigations to establish a diagnosis of death due to cardioinhibitory reflex.

Paraplegia increased cardiac NGF content, sympathetic tonus, and the susceptibility to ischemia-induced ventricular tachycardia in conscious rats

Midthoracic spinal cord injury is associated with ventricular arrhythmias that are mediated, in part, by enhanced cardiac sympathetic activity. Furthermore, it is well known that sympathetic neurons have a lifelong requirement for nerve growth factor (NGF). NGF is a neurotrophin that supports the survival and differentiation of sympathetic neurons and enhances target innervation. Therefore, we tested the hypothesis that paraplegia is associated with an increased cardiac NGF content, sympathetic tonus, and susceptibility to ischemia-induced ventricular tachyarrhythmias. Intact and paraplegic (6-9 wk posttransection, T(5) spinal cord transection) rats were instrumented with a radiotelemetry device for recording arterial pressure, temperature, and ECG, and a snare was placed around the left main coronary artery. Following recovery, the susceptibility to ventricular arrhythmias (coronary artery occlusion) was determined in intact and paraplegic rats. In additional groups of matched intact and paraplegic rats, cardiac nerve growth factor content (ELISA) and cardiac sympathetic tonus were determined. Paraplegia, compared with intact, increased cardiac nerve growth factor content (2,146 +/- 286 vs. 180 +/- 36 pg/ml, P < 0.05) and cardiac sympathetic tonus (154 +/- 4 vs. 68 +/- 4 beats/min, P < 0.05) and decreased the ventricular arrhythmia threshold (3.6 +/- 0.2 vs. 4.9 +/- 0.2 min, P < 0.05). Thus altered autonomic behavior increases the susceptibility to ventricular arrhythmias in paraplegic rats.

Modification of ventricular tachycardia by carotid sinus massage

A case of ventricular tachycardia (VT) was aggravated by carotid sinus massage in a woman with an old myocardial infarction. The patient presented with a wide QRS complex tachycardia with a rate of 143 beats/min, which fulfilled the classic and newer electrocardiographic criteria for the diagnosis of VT. Carotid sinus massage performed during the tachycardia resulted in its conversion to another, wide QRS complex tachycardia, with different morphology and a faster rate resembling ventricular flutter. This latter tachycardia was converted to sinus rhythm by a thump on the patient's chest. The initial tachycardia was proved to be of ventricular origin by electrophysiologic study at a later stage during a recurrence. Vagal stimulation probably resulted in inhomogeneous increase of the ventricular refractory period, creating conditions for a reentrant circuit other than the preexisting one and for the emergence of VT with a different QRS morphology and rate. Although termination and/or initiation of VT by carotid sinus massage has been reported in the past, modification of VT by carotid sinus massage has not been described previously.

Autonomic nervous system responses to exercise in relation to ventilatory threshold

We introduce our recent approach to study autonomic nervous system control of heart rate during exercise by means of heart rate variability (HRV) spectral analysis with special reference to its relationship to ventilatory threshold (Tvent). The rationale for the study was that HRV has been shown to reflect (cardiac) parasympathetic and sympathetic nervous system (PNS and SNS, respectively) activity, together with the underlying complexity of cerebral autonomic system in terms of fractal dimension (DF) of HRV time series. The experimental results showed that PNS was markedly reduced below Tvent, that the rate of change in sympathoadrenal activity indicators (plasma norepinephrine and epinephrine concentrations and SNS indicator) was enhanced above Tvent, and that these changes in PNS and SNS indicators were associated with the appearance of the low-dimensional (low DF) dynamics that might reflect less complex autonomic activity. These findings have been considered with respect to implication for clinical cardiology.

"The anti-Ashman maneuver": a bedside method for distinguishing aberrancy from ventricular ectopy

This is a report of a patient who develops new onset atrial fibrillation in the postoperative setting which is further complicated by the presence of wide beats in singles, pairs, and short runs. Presented are the differential diagnosis of these wide beats and a simple bedside maneuver to help distinguish their origin.

The role of enhanced vagal activity on ischemic ventricular tachycardia: pharmacologic basis of inefficiency

The effects of pharmacologic modulation of vagal activity on ischemic ventricular tachycardia were evaluated in 21 conscious dogs after permanent left anterior descending coronary artery (LAD) occlusion. Studies were done on spontaneous ventricular tachycardia (cycle length 383 +/- 100 msec, n = 21), 24 to 72 hours after LAD occlusion, and on inducible sustained monomorphic ventricular tachycardia (cycle length 251 +/- 30 msec, n = 6), 4 to 7 days after LAD occlusion. Edrophonium (1 mg/kg intravenously), a cholinesterase inhibitor, and methacholine (0.1 to 1 mg intravenously), a muscarinic agonist, had no significant effect on the rate or QRS morphology of either type of tachycardia, despite severe slowing of the sinoatrial rate. Similarly, atropine (up to 60 micrograms/kg intravenously) had no effect on the rate and QRS morphology of either type of tachycardia. In an attempt to enhance myocardial drug delivery to the ischemic and infarcted left ventricle, edrophonium (1 mg/kg) and methacholine (0.1 to 0.2 mg) were injected retrogradely through the great cardiac vein. This did not impart any significant therapeutic advantage over the systemic intravenous route. Sympathetic beta blockade did not affect the therapeutic outcome (n = 5) with either edrophonium or methacholine. It is concluded that direct or indirect enhancement of cardiac vagal activity has no effect on ischemic ventricular tachycardia in this model of subacute myocardial infarction. The lack of efficacy appears to be independent of myocardial drug delivery to ischemic ventricular site(s) and background sympathetic activity. Such a lack of efficacy may be caused by ischemia-mediated degeneration of vagal nerve terminals, by altered responsiveness of muscarinic receptors at infarcted arrhythmogenic myocardial sites, or both.

Termination of ventricular tachycardia by carotid sinus stimulation

A 56-year-old white male developed sustained ventricular tachycardia which was terminated by carotid sinus stimulation. Intracardiac electrophysiologic study reproduced the tachycardia which was repeatedly terminated by carotid massage. This report, together with others reviewed here, suggests that tachycardia termination by simple carotid stimulation does not always prove a supraventricular origin.

Propranolol blocks ventricular refractory period changes with orthostatic stress in humans

The purpose of this study was to test the hypothesis that orthostatic stress shortens the right ventricular effective refractory period by reflex activation of beta-adrenergic receptors. Twelve patients undergoing electrophysiologic testing for standard clinical indications were studied. After a full electrophysiologic study, patients underwent graded lower body negative pressure before and after administration of either propranolol (0.2 mg/kg intravenously) in Group I or atropine (0.035 mg/kg intravenously) in Group II. Before the addition of drugs, lower body negative pressure produced decreases in systolic blood pressure and significant increases in sinus rate. The effective refractory period shortened from 214 +/- 8 (mean +/- SEM) to 206 +/- 7 ms at -40 cm H2O and to 197 +/- 4 ms at -60 cm H2O lower body negative pressure. After propranolol, Group I patients had no change in right ventricular effective refractory period despite similar changes in sinus rate and systolic blood pressure. In group II patients, atropine did not alter effective refractory period responses to lower body negative pressure. Thus, reflex adjustments to orthostatic stress result in shortening of right ventricular effective refractory period mediated by way of beta-adrenergic mechanisms. These findings constitute the first evidence that sympathetic influences mobilized by the body can directly modulate ventricular electrophysiologic changes.

Modulation of an idioventricular rhythm by vagal tone

A 28 year old man with a stable permanent idioventricular rhythm of 80 to 85 beats/min, with all the characteristics of a pacemaker, is described. This pacemaker was slowed by maneuvers that enhanced vagal tone, including carotid sinus massage, the postrelease phase of the Valsalva maneuver and phenylephrine. The pacemaker was also slowed by a cholinesterase inhibitor (edrophonium hydrochloride) and accelerated by a muscarinic receptor blocking drug (hyoscine butylbromide). The actions of these maneuvers and agents were independent of sympathetic tone as propranolol pretreatment did not alter their effects. Similarly, propranolol did not affect the pacemaker rate. The pacemaker was not dependent on a slow inward current because verapamil did not affect its rate. The pacemaker accelerated in response to increased sympathetic tone induced by exercise and upright tilting and to the adrenergic agonist isoproterenol. The pacemaker was localized to the high posterior septal region of the left ventricle underneath the mitral valve. This report describes in a man an idioventicular pacemaker that is innervated by sympathetic and vagal fibers and responsive to alterations in tone of both limbs of the autonomic nervous system. It offers the first clear proof that a ventricular pacemaker can be innervated and controlled by the vagus nerve and provides its location.

A wide, complex look at cardiac dysrhythmias

The diagnosis and treatment of cardiac dysrhythmias answers the following four questions: Is the patient stable? Is the rate fast or slow? Are the ventricular complexes wide or narrow? Is the rhythm regular or irregular? The most common narrow complex regular tachycardias are sinus tachycardia, atrial flutter, atrial tachycardia that blocks, and paroxysmal supraventricular tachycardia. Carotid sinus massage is useful in differentiation. Irregular narrow-complex tachycardias are usually atrial fibrillation. An ultra-rapid wide-complex or polymorphous irregular tachycardia is likely to be atrial fibrillation with ventricular preexcitation. Wide-complex regular tachycardias present a special challenge, since wide beats may result from supraventricular or ventricular impulse formation. Ventricular tachycardia is more likely than supraventricular tachycardia in the presence of underlying ischemic heart disease, atrioventricular dissociation, fusion or capture beats, or a very broad (greater than .14 seconds) QRS complex. Still, misdiagnosis is common; the most costly mistake is over-diagnosis of SVT. In emergencies, where vital organ hypoperfusion is present, the origin of the impulse and the name of the dysrhythmia are unimportant. With the exception of sinus tachycardia, all life-threatening, rapid tachycardias should be terminated by electrical cardioversion.

Carotid sinus massage. Its diagnostic and therapeutic value in arrhythmias

Carotid sinus massage is a simple bedside maneuver that helps to clarify the type and sometimes also the mechanism of different rhythm disturbances. The major indication for carotid sinus massage is the diagnosis of tachyarrhythmias in which the atrial activity is either absent or intermittently present. Carotid sinus massage is also useful in some patients with normal heart rates; increased vagal tone may normalize a bundle branch block or localize the site of type I second-degree atrioventricular block and can be used for evaluation of the sensing function of permanent pacemakers. Carotid sinus massage is also an important diagnostic procedure in patients with suspected hypersensitivity of the carotid sinus. Massage of the carotid sinus is contraindicated in patients with diseased carotid arteries because of the risk of cerebrovascular accident. In rare instances, carotid sinus massage may initiate ventricular tachycardia.