Which one of the following is true about “pacemaker syndrome”?
Symptoms usually include fatigue, dizziness, and hypotension. Pacemaker syndrome is caused by pacing the ventricle asynchronously, which results in AV dissociation or VA conduction. Symptoms consist of fatigue, dizziness, dyspnea, and weakness, with or without hypotension. The mechanism is believed to be related in part to atrial contraction against a closed AV valve and release of atrial natriuretic peptide. It occurs with ventricular pacing and therefore is worsened by increasing pacing rate and relieved by allowing intrinsic conduction (if present) by lowering the pacing rate, programming rate hysteresis, or upgrading to a dual-chamber system. Therapy with fludrocortisone and other volume-expansion modalities is not helpful.
Of the following patients, who is the most likely to carry the diagnosis of sick sinus syndrome (SSS)?
A 73-year-old man with persistent AFib and a ventricular rate of 40 bpm during peak treadmill test. The 73-year-old man with AFib and slow ventricular rate during exercise is the classic example of SSS. This usually indicates degenerative disease of the cardiac conduction system involving the AV node as well as the sinus node. Function of the sinus node can only be assessed after AFib has been terminated, usually by DC cardioversion. In this patient’s case, it would not be uncommon to manifest a long postconversion pause, followed by either marked sinus bradycardia or complete sinus node arrest with a resulting junctional or ventricular escape rhythm (hopefully) following cardioversion. The finding of sinus arrhythmia varying by 15 bpm in an older patient, the profound nocturnal bradycardia in young athletes, and the sinus pauses in young patients are related mostly to a high vagal tone and do not indicate sinus node disease.
A 76-year-old patient with dilated cardiomyopathy and LBBB on baseline ECG is undergoing evaluation for syncope. Placement of a catheter near his bundle during EP testing is most likely to:
Induce complete heart block (CHB). Patients with true complete LBBB are at risk for developing transient CHB during catheter manipulation in the septal region of the tricuspid valve. This is caused by transient traumatic block of the right bundle branch. A similar scenario can result when placing a Swan-Ganz catheter in patients with LBBB.
A 25-year-old patient with a history of depression is brought to the emergency room after ingesting some of her mother’s prescription medications, including diltiazem and metoprolol. Her pulse rate is 25 bpm, and her BP is 90/50 mmHg. Her ECG shows sinus bradycardia and highgrade AV block.
In preparation for temporary pacemaker placement, which of the following is most likely to be effective?
IV glucagon. This patient has an overdose of diltiazem and metoprolol. These drugs slow sinoatrial and AV conduction. Calcium and magnesium have no effect in reversing these bradycardic effects. Isuprel and atropine are not likely to overcome the β-blockade of metoprolol. IV glucagon acts on a specific receptor. This results in an increase in intracellular cyclic adenosine monophosphate, which enhances both sinoatrial and AV node conduction despite the presence of β-blockade.
A young patient is admitted to the intensive care unit with amitriptyline overdose. Three hours after gastric lavage, he develops hypotension and wide complex tachycardia that is recurrent despite cardioversion.
Appropriate management includes which of the following?
IV hypertonic sodium bicarbonate. Amitriptyline has sodium channel– blocking properties and induced QRS widening and VT. Increasing the extracellular sodium concentration by the administration of sodium bicarbonate decreases the association of this drug with the sodium channel.
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