Guidelines Summary
2018 ACC/AHA/HRS guidelines
The guideline on the evaluation and management of bradycardia and cardiac conduction delay was released in November 2018, by the American College of Cardiology (ACC), the American Heart Association (AHA), and the Heart Rhythm Society (HRS). [40, 41]
The guideline’s top 10 key messages for assessing and treating patients with bradycardia or other disorders of cardiac conduction delay are provided below.
Sinus node dysfunction is most often related to age-dependent progressive fibrosis of the sinus nodal tissue and surrounding atrial myocardium leading to abnormalities of sinus node and atrial impulse formation and propagation and will therefore result in various bradycardic or pause-related syndromes.
Sleep disorders of breathing and nocturnal bradycardias are relatively common. Treatment of sleep apnea reduces the frequency of these arrhythmias and also may offer cardiovascular benefits. The presence of nocturnal bradycardias should prompt consideration for screening for sleep apnea, beginning with solicitation of suspicious symptoms. However, nocturnal bradycardia is not in itself an indication for permanent pacing.
The presence of left bundle branch block on electrocardiogram markedly increases the likelihood of underlying structural heart disease and of diagnosing left ventricular (LV) systolic dysfunction. Echocardiography is usually the most appropriate initial screening test for structural heart disease, including LV systolic dysfunction.
In sinus node dysfunction, there is no established minimum heart rate or pause duration where permanent pacing is recommended. It is important to establish a temporal correlation between symptoms and bradycardia when determining whether permanent pacing is needed.
In patients with acquired second-degree Mobitz type II atrioventricular (AV) block, high-grade AV block, or third-degree AV block not caused by reversible or physiologic causes, permanent pacing is recommended regardless of symptoms. For all other types of AV block, in the absence of conditions associated with progressive AV conduction abnormalities, permanent pacing should generally be considered only in the presence of symptoms that correlate with AV block.
In patients with an LV ejection fraction between 36% and 50% and AV block, who have an indication for permanent pacing and are expected to require ventricular pacing over 40% of the time, techniques that provide more physiologic ventricular activation (eg, cardiac resynchronization therapy [CRT], His bundle pacing) are preferred to right ventricular pacing to prevent heart failure.
Because conduction system abnormalities are common after transcatheter aortic valve replacement (TAVR), recommendations on postprocedure surveillance and pacemaker implantation are made in this guideline.
In patients with bradycardia who have indications for pacemaker implantation, shared decision-making and patient-centered care are endorsed and emphasized in this guideline. Treatment decisions are based on the best available evidence and on the patient’s goals of care and preferences.
Using the principles of shared decision-making and informed consent/refusal, patients with decision-making capacity or his/her legally defined surrogate have/has the right to refuse or request withdrawal of pacemaker therapy, even if the patient is pacemaker dependent, which should be considered palliative, end-of-life care, and not physician-assisted suicide. However, any decision is complex, should involve all stakeholders, and will always be patient specific.
Identifying patient populations that will benefit the most from emerging pacing technologies (eg, His bundle pacing, transcatheter leadless pacing systems) will require further investigation as these modalities are incorporated into clinical practice.
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This 12-lead electrocardiogram (ECG) is from an asymptomatic girl aged 10 years, which was brought to our attention because of the irregularity of the P-P intervals. This ECG shows sinus arrhythmia at a rate of 65-75 beats per minute. The P waves all originate from the sinus node (SN) because they have a positive axis (upright) in leads I, II, and aVF. The PR interval is 104ms, and the QRS is narrow at 86ms, with a normal axis of 64°. The corrected QT (QTc) interval measures 402ms. Therefore, this is a normal ECG.
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Below is an electrocardiogram (ECG) of a girl aged 2 years who was referred to the clinic by a pediatrician for evaluation of a heart murmur. This ECG shows atrial rhythm originating most likely from the lower left atrium (P waves are inverted in lead I and are positive in II and aVF, with a frontal axis of 124°). The PR interval measures 113 ms, and the QRS is narrow at 90 ms. Right ventricular (RV) conduction delay is shown and is best seen in the precordial leads V1 and V2. The QRS frontal axis shows right axis deviation (reference range for a child aged 2 years is 0-110°). The patient does not have RV hypertrophy by voltage criteria. The inverted T waves in V1 are a normal finding at this age. An echocardiogram showed a moderately sized atrial septal defect. Nonsinus atrial rhythm is not a synonym of sinus node dysfunction.
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This is a 12-lead electrocardiogram (ECG) from a boy aged 12 years with a history of syncope. This patient was healthy until 1 month earlier, when he started to experience episodes of lightheadedness. The ECG shows sinus arrhythmia (bradycardia) at a rate of 50-79 beats per minute, with a PR interval of 136 ms. Two junctional escape beats are present after a prolonged pause. The QRS is narrow at 85 ms, with a normal frontal axis of 70°. The corrected QT interval (QTc) is 411 ms. A later electrophysiologic study showed prolonged sinus node recovery time (SNRT) and sinoatrial conduction time (SACT). Because of the patient's symptoms and his sinus node (SN) dysfunction, he received an atrial pacemaker. If this 12-lead ECG had been recorded from an asymptomatic patient, the findings would be considered within normal limits and no further workup would be indicated. In this case, the lightheadedness and, ultimately, the syncope defined sick sinus syndrome, with the patient requiring pacemaker therapy.
