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Kusumoto et al 2018 Bradycardia Clinical Practice Guidelines August 20, 2019 Circulation. 2019;140:e382–e482. DOI: 10.1161/CIR.0000000000000628 e414 CLINICAL STATEMENTS AND GUIDELINES a different indication or reason such as evaluation of inducibility of ventricular arrhythmia or presence of His-Purkinje conduction abnormality often in the setting of syncope or nonsustained ventricular tachycardia with reduced left ventricular function.S5.4.3-8,S5.4.3-9 In such cases, sinus node function could be evaluated at little to no added risk to the patient and can provide adjunctive information in patients with symptoms suggestive of bradycardia. 2. Patients with suspected SND sometimes do not have a definitive diagnosis even after undergoing a battery of initial noninvasive tests. EPS can be considered in such cases to help support or refute the diagnosis of SND, and the findings can be used to guide the therapy, provided that the data are used in conjunction with other clinical findings. The most well-known method to assess sinus node function is the measurement of SNRT. In brief, the atrium is paced using a properly positioned catheter at a predetermined rate for a given duration (30- 60 s) of time. The interval to the first spontaneous atrial depolarization from the last paced beat is measured after the pacing is stopped. Corrected SNRT is an indexed value obtained by subtracting the baseline R-R interval from the longest obtained SNRT. An abnormal corrected SNRT is considered to be any value >500 to 550 ms.S5.4.3-4 The SACT is less commonly used but can be calculated by either continuous pacing at different intervals, with premature atrial stimuli, or direct recording of sinus node electrograms.S5.4.3-10 3. Asymptomatic patients with sinus bradycardia should not undergo EPS because the risk of invasive testing outweighs the potential for clinical benefit. Although risk of EPS is likely low in the modern era, an older study reported a complication rate of 8%, mainly hematoma and induction of AF.S5.4.3-6 In an asymptomatic patient, an incidental finding of abnormal SNRT or SACT has no clinical importance.S5.4.3-7 5.4.4. Permanent Pacing for Chronic Therapy/Management of Bradycardia Attributable to SND Recommendations for Permanent Pacing for Chronic Therapy/ Management of Bradycardia Attributable to SND Referenced studies that support recommendations are summarized in Online Data Supplements 24 and 25. COR LOE Recommendations I C-LD 1. In patients with symptoms that are directly attributable to SND, permanent pacing is indicated to increase heart rate and improve symptoms.S5.4.4-1,S5.4.4-2 I C-EO 2. In patients who develop symptomatic sinus bradycardia as a consequence of guidelinedirected management and therapy for which there is no alternative treatment and continued treatment is clinically necessary, permanent pacing is recommended to increase heart rate and improve symptoms. IIa C-EO 3. For patients with tachy-brady syndrome and symptoms attributable to bradycardia, permanent pacing is reasonable to increase heart rate and reduce symptoms attributable to hypoperfusion. IIa C-EO 4. In patients with symptomatic chronotropic incompetence, permanent pacing with rateresponsive programming is reasonable to increase exertional heart rates and improve symptoms. IIb C-LD 5. In patients with symptoms that are likely attributable to SND, a trial of oral theophylline may be considered to increase heart rate, improve symptoms, and help determine the potential effects of permanent pacing.S5.4.4-3,S5.4.4-4 Synopsis Permanent cardiac pacing is indicated to alleviate the symptoms of cerebral hypoperfusion attributable to bradycardia when other potential treatable or reversible etiologies have been excluded. Symptomatic SND is the most common indication for permanent pacing, followed closely by atrioventricular block. Often the best response to pacing therapy is demonstrated when an unequivocal correlation has been established between symptoms and bradycardia. The benefit of pacing in SND is mainly QOL improvement. A strategy for managing a patient with SND is provided in Figure 6. Recommendation-Specific Supportive Text 1. When there is direct evidence of symptom correlating with sinus bradycardia or pauses, permanent cardiac pacing will lead to clinical improvement. Such a temporal symptom-bradycardia correlation is regarded as the gold standard of diagnosis and confers the highest likelihood of response to therapy. Prolonged sinus pauses can also be debilitating and are associated with significant morbidity because of recurrent presyncope or syncope of sudden and unpredictable onset. Permanent cardiac pacing will also treat such symptomatic pauses.S5.4.4-1,S5.4.4-2 2. Beta-blocking and calcium channel–blocking drugs are commonly used in patients with cardiovascular disorders. Negative chronotropic drugs exacerbate SND symptoms by diminishing the slope of phase 4 diastolic depolarization, Recommendations for Permanent Pacing for Chronic Therapy/ Management of Bradycardia Attributable to SND (Continued) COR LOE Recommendations Downloaded from http://ahajournals.org by on October 7, 2026