![]() ![]() SND and/or tachy-brady syndrome can result from cardiac surgery, particularly associated with right atriotomy. Tachy-brady syndrome may present with rapid palpitations during atrial arrhythmias and lightheadedness, dizziness, near syncope, and/or syncope during postconversion pauses. Hemodynamic tolerance of SB is a function of heart rate (a rate of < 30 bpm is usually not well tolerated), underlying disease (less tolerated with poor ventricular function), and age (better tolerated in those < 50 years old). SND, including chronotropic incompetence, can impair cardiac output or exacerbate heart failure and can be associated with or trigger atrial arrhythmias (e.g., atrial fibrillation) and ventricular arrhythmias (e.g., torsades de pointes). When present, symptoms may include fatigue, effort intolerance, palpitations, dizziness, lightheadedness, near syncope, syncope, dyspnea, and angina. SB is asymptomatic in the vast majority of patients. SB can be exacerbated by drugs that are used to slow AV node conduction during atrial arrhythmias. Clinical syndromes, such as neurocardiogenic syncope and some specific rhythm disorders such as tachy-brady syndrome, can be associated with symptomatic bradycardia as well as symptoms caused by rapid ventricular rates during atrial fibrillation or flutter severe SB or sinus arrest can occur after spontaneous conversion prior to recovery of the sinus node. SB is usually associated with inferior-posterior infarction (caused by increased vagal tone from stimulation of vagal afferents, the Bezold-Jarisch reflex). The bradycardia usually resolves without the need for chronic therapy. SB occurs in 14% to 36% of MIs and can be associated with AV block. SB is usually benign but can be associated with certain conditions and diseases, including hypothyroidism, vagal stimulation, carotid sinus hypersensitivity, increased intracranial pressure, myocardial infarction (MI), and drugs such as β-adrenergic blockers (including those used for glaucoma), calcium channel blockers, amiodarone, sotalol, clonidine, lithium, and parasympathomimetic drugs. SB is often associated with sinus arrhythmia, escape rhythms (junctional and ventricular), accelerated rhythms (junctional and ventricular), atrial arrhythmias, WAP, or SA or AV Wenckebach-like periods. The combination of a tachycardia that is suddenly followed by a bradycardia is characteristic of tachy-brady syndrome. The tachycardia is followed by a 3.4-second pause and then sinus bradycardia. This rhythm strip tracing shows an atrial tachyarrhythmia (atrial flutter/tachycardia) that suddenly terminates. WAP should not be confused with “multifocal atrial rhythm” (see Fig. WAP is often seen in patients with sinus arrhythmia. In WAP, there are varying exit points of the sinus impulse from the sinus node or impulses that originate from the sinus node and wander from the node to the low atrium and back. 1.3 ) occurs in association with high vagal tone and is a benign rhythm. Higher resting sinus rates have been associated with increased risk for overall mortality. Patients who are in good physical condition generally have more gradual acceleration in sinus rate with exercise and a rapid slowing of the sinus rate at the end of exercise, compared with less physically fit individuals or individuals with heart disease. Ventriculophasic sinus arrhythmia is present when alterations in the sinus rate are due to atrioventricular (AV) block: The P-P intervals enclosing a QRS complex are shorter than P-P intervals not enclosing a QRS complex.Ī change in sinus rate can be gradual or abrupt and can occur with change in body position and exercise. Various forms of sinus arrhythmia exist, including a non–respiration-dependent form that may indicate sinus node dysfunction (SND). ![]() Sinus arrhythmia is often related to respiratory cycles. This lead V 1 and II rhythm strip shows normal sinus rhythm with sinus arrhythmia, in which the P-P intervals vary by greater than 0.16 seconds. ![]()
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