Narrow-complex tachycardia

Stable monomorphic VT, HR control in a fib, A/ reentrant narrow complex tachycardia 20 mg/min IV until one of these ar hythmia stopped, hypotension, QRS... 

Adenosine is the treatment of choice for diagnosis and reversal of supraventricular arrhythmias. Verapamil is an alternative for the management of narrow complex tachycardias. Amiodarone is the most effective drug at reversing atrial fibrillation, and in prevention of ventricular arrhythmias, but has several adverse effects. 

A 38-year-old man was given intravenous adenosine 6 mg for a narrow-complex tachycardia (20). Within about 1 minute his heart rate fell from 230/minute to bradycardia and then asystole. Cardiopulmonary resuscitation was ineffective. At autopsy there was a 75% occlusion of one of the coronary arteries (unspecified). 

A 56-year-old man was given adenosine 12 mg for a narrow-complex tachycardia on four occasions, and on each occasion developed transient atrial fibrillation for a few minutes thereafter. He had a concealed left-sided accessory pathway, which was successfully ablated (23). 

Bakshi F, Barzilay Z, Paret G. Adenosine in the diagnosis and treatment of narrow complex tachycardia in the pediatric intensive care unit. Heart Lung 1998 27(l) 47-50. 

A male infant, whose narrow-complex tachycardia at birth had responded to adenosine, was treated with digoxin and 1 week later, during transesophageal electrophysiology with isoprenaline, developed coarse ventricular fibrillation after the induction of a supraventricular tachycardia (45). The serum digoxin concentration was not measured. The isoprenaline was withdrawn and the dysrhythmia resolved spontaneously at 160 seconds. 

Drug overdose Life-threatening flecainide intoxication in a 2-year-old toddler occurred when syringes used for oral administration were accidentally reversed, producing a fivefold flecainide overdose 3 hours after drug administration he developed a bradycardia of 50/minute and had a cardiopulmonary arrest, requiring resuscitation and adrenaline, after which the bradycardia recurred, followed by a wide-complex tachycardia that converted rapidly to a narrow-complex tachycardia after bolus intravenous adrninistration of sodium bicarbonate [60 ]. He then remained hemo-dynamicaUy stable and in sinus rhjflhm. The serum flecainide concentration was 0.7 mg/1. 

See Irregular Narrow-Complex Tachycardia (box 11). Upn-excHod aelalf Madon (AP+WFW ... 

Management of Narrow Complex Stable Supraventricular Tachycardia (QRS < 0.12 s)... 

Management of Narrow Complex Stable Supraventricular Tachycardia... 

Differentiate PSVT from narrow-complex ventricular tachycardia prior to IV administration failure fo do so has resulted in fatalities... 

Adenosine and adenosine triphosphate (ATP), its phosphorylated derivative, have been used to treat acute paroxysmal supraventricular tachycardias and adenosine has also been used in the diagnosis of narrow-and broad-complex tachycardias (SEDA-16,176). 

Most commonly, PSVT is a rapid, narrow-QRS-complex tachycardia, regular in rhythm, that starts and stops abruptly. Atrial activity, although present, is difficult to ascertain on surface ECG because P waves are "buried" within the QRS complex or T wave. 

A 36-year-old woman with a history of hypothyroidism became lethargic after taking an overdose of diphenhydramine. Her serum concentration was 1200 ng/ml. She developed generalized seizures, which continued for 30 minutes despite intravenous lorazepam 8 mg. A propofol infusion terminated the seizures. An electrocardiogram showed a wide complex tachycardia with a QRS duration of 12 ms, which narrowed after administration of intravenous sodium bicarbonate 200 mmol. She recovered within 2 days. 

The differential diagnosis of this regular narrow QRS complex rhythm with 1 1 AV relationship at such a short interval between R and P waves is essentially typical AV node reentrant tachycardia (AVNRT) vs. atrial tachycardia with a severe first degree AV block. The interval between each R wave and subsequent P wave appears fixed. An atrial or sinus tachycardia does not have this fixed relationship between R and subsequent P wave, and typically may display variation in the interval between them. Thus, from the EGMs this is most likely typical AVNRT. 

A 72-year-old woman, treated with flecainide and haloperidol, presented with breathlessness due to regular tachycardia with wide QRS complex. The ECG showed a regular monomorphic tachycardia at ISObpm, no apparent P wave, QRS duration of 240 ms with a left bxmdle branch block. An intravenous bolus of 10 mg ATP was administered. However, it turned out to be ineffective. The diagnosis of tachycardia induced by flecainide overdose was considered and treatment with 8.4% sodium bicarbonate was initiated. The sodium bicarbonate infusion caused immediate narrowing of the patienPs QRS and the ECG showed sinus rhythm. Blood samples confirmed flecainide overdose [27]. 

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