Chapter 276 - Supraventricular Tachyarrhythmias Flashcards
Supraventricular tachyarrhythmias are always accompanied with narrow QRS-complexes.
True or False?
False.
“Most produce narrow QRS-complex tachycardia (QRS activation less than 120ms) characteristic of ventricular activation over the Purkinje system. Conduction block i nthe left or right bundle branch or activation of the ventricles from an accessory pathway produces a wide QRS complex during supraventricular tachycardia that must be distinguished from ventricular tachycardia.”
Which symptoms might occur during a supraventricular tachyarrhythmia?
“Symptoms of supraventricular arrhythmia vary depending on the rate, duration, assocaited heart disease, and comorbidities and include palpiations, chest pain, dyspnea, dimished exertional capcity and occasionally syncope.”
Name two conditions with supraventricular tachyarrhythmia that rarely might be associated with sudden death.
“Rarely, a supraventricular arrhythmia precipitates cardiac arrest in patients with the Wolff-Parkinson-White syndrome or severe heart disease, such as hypertrophic cardiomyopathy.”
Where is sinus node localized?
“The sinus node is coprised of a group of cells dispersed within the superior aspect of the thick ridge of muscle known as the crista terminalis where the posterior smoooth atrial wall derived from the sinus venosus meets the trabeculated anterior portion of the right atrium.”
How does one explain the fact that p waves are usually taller during sinus tachycardia in comparison to normal sinus rhythm?
“Sinus tachycardia (>100beats/min) typically occurs in response to sympathetic stimulation and vagal withdrawal, whereby the rate of spontaneous depolarization of the sinus node increases and the focus of earlist activation within the node typically shifts more leftward and closer to the superior septal aspect of the crista terminalis, thus producing taller p waves in the inferior limb leads when compared to normal sinus rhythm.”
Which indicators might help one differentiate sinus tachycardia from focal atrial tachycardia?
“Sinus tachycardia can be difficult to distinguish from focal atrial tachycardia that originates from a focus near the sinus ndoe. A causative factor (such as exertion) and a gradual increase and decrease in rate favors sinus tachycardia, whereas an abrupt onset and offset favor atrial tachycardia. The distinction can be difficult and occasionally requires extended ECG monitoring or even invasive electrophysiology study.”
Which patients are mostly affected with inappropriate sinus tachycardia and what are the usual clinical manifestations?
“Affected individuals are often women in the third or fourth decade of life. Fatigue, dizziness, and even syncope may accompany palpitations, which can be disabling. Additional symptoms of chest pain, headaches, and gastrointestinal upset are common.”
Inappropriate sinus tachycardia is frequently misdiagnosed as physiologic sinus tachycardia with an anxiety disorder.
True or False?
True.
How does one treat inappropriate sinus tachycardia?
“Careful titration of beta blockers and/or calcium channel blockers may reduce symptoms. Clonidine and serotonin reuptake inhibitors have also been used. Ivabradine, a drug that blocks the If current causing sinus node depolarization, is promising but is not approved for use in the United States. Catheter ablation of the sinus node has been used, but long-term control of symptoms is usually poor, and it often leaves young individuals with a permanent pacemaker.”
Describe the postural orthostatic tachycardia syndrome and its treatment.
“When symptomatic sinus tachycardia occurs with postural hypontesion, the syndrome is called postural orthostatic tachycardia syndrome (POTS). Symptoms are often similar to those in patients with inappropriate sinus tachycardia. POTS is sometimes due to autonomic dysfunction following a viral illness and mayu resolve spontaneously over 3-12 months. Volume expansion with salt supplementation, oral fludrocortisone, compression stockings, and the a-agonist midodrine, often in combination, can be helpful. Exercise training has also been purported to improve symptoms.”
