Bradycardia and permanent pacing — structured written assessment

SAQ 1 (10 marks)

Practice scenario. A 66-year-old man is brought to the emergency department after two collapses at home. An ECG a year ago was normal. He is pale and confused. HR 32/min, BP 78/46 mmHg.^[7] The ECG shows complete AV block with a broad-QRS escape rhythm and no ST elevation. He has no history of heart transplantation and takes no drug that slows or blocks AV conduction.^[7][4]

1. Which ANZCOR features in this man call for immediate treatment, and which indicate a potential risk of asystole? (3)^[7]
2. Give the ANZCOR drug sequence with doses, and say when pacing is needed. (3)^[7]
3. Outline temporary pacing under the 2021 ESC pacing guideline: the recommendations with their class, and the risks that argue for keeping it short. (2)^[1]
4. Which tests look for a reversible cause and for structural heart disease, under ESC 2021 and ACC/AHA/HRS 2018? (2)^[1][4]

Model answers — SAQ 1

1. Immediate treatment: ANZCOR lists systolic BP below 90 mmHg, heart rate below 40/min, ventricular arrhythmia and heart failure as adverse signs that suggest a need for immediate treatment; he has the first two.^[7] His collapses and confusion fit symptomatic bradycardia: ANZCOR lists syncope and dizziness among the common symptoms, and the ACC/AHA/HRS 2018 definition includes syncope and confusional states resulting from cerebral hypoperfusion attributable to slow heart rate.^[7][4] Potential risk of asystole: ANZCOR says it is indicated by any of recent asystole, Mobitz II AV block, complete AV block (especially with broad QRS or an initial heart rate below 40/min) and ventricular standstill over 3 s; he has complete AV block with both aggravating features.^[7]
2. While assessing, give oxygen, obtain IV access and record a 12-lead ECG, without delaying treatment.^[7] Atropine is the initial treatment: 500–600 mcg IV, repeated as necessary every 3–5 min up to a total dose of 3 mg.^[7] If this fails, low-dose adrenaline (as a bolus or as an infusion) is the second-line agent, usually 2–10 mcg/min to maintain a satisfactory heart rate (stable heart rate with a mean arterial pressure of 70 mmHg).^[7] Other drugs ANZCOR lists include isoprenaline 2–5 mcg/min, dopamine 2–5 mcg/kg/min, theophylline and glycopyrrolate.^[7] Patients who fail to respond to drugs, or who are at high risk of asystole as he is, may require electrical pacing by an internal or external route.^[7] External pacing through defibrillator pads is usually set to demand at 70–80 beats per minute, starting low (e.g. 30 mA) and increasing until electrical capture with established output occurs; it may be uncomfortable.^[7] ACC/AHA/HRS 2018 notes that block within or below the His bundle will not respond to atropine but will sometimes improve with catecholamines.^[4]
3. ESC 2021: temporary transvenous pacing is recommended for haemodynamic-compromising bradyarrhythmia refractory to IV chronotropic drugs (Class I, Level C), and in haemodynamic-compromising bradyarrhythmia, transcutaneous pacing should be considered when temporary transvenous pacing is not possible or available (Class IIa, Level C).^[1] Temporary transvenous pacing should also be considered when immediate pacing is indicated and the indication is expected to be reversible, such as myocardial ischaemia, myocarditis, electrolyte disturbances, toxic exposure or after cardiac surgery (Class IIa, Level C), and as a bridge when permanent implantation is not immediately available or possible due to concomitant infection (Class IIa, Level C).^[1] For long-term temporary transvenous pacing, an active fixation lead inserted through the skin and connected to an external pacemaker should be considered (Class IIa, Level C).^[1] Transvenous temporary pacing carries a high risk of procedure-related complications (e.g. cardiac perforation, bleeding, malfunction, arrhythmias, accidental electrode displacement) and of complications of immobilisation (e.g. infection, delirium, thrombotic events), and previous temporary pacing is associated with an increased risk of permanent pacemaker infection.^[1] So it should be avoided if possible and, when required, left in situ for as short a time as possible; if the patient meets permanent pacing criteria, implantation should be performed promptly.^[1] Transcutaneous pacing is fast and non-invasive but less stable than transvenous pacing and needs continuous sedation, so ESC 2021 limits it to emergencies or when no other option is available, under close haemodynamic monitoring.^[1]
4. ESC 2021: in addition to pre-implantation tests (complete blood counts, prothrombin time, partial thromboplastin time, serum creatinine and electrolytes), specific tests are recommended when a reversible cause is clinically suspected (e.g. thyroid function, Lyme titre, digitalis level, potassium, calcium and pH) to diagnose and treat these conditions (Class I, Level C).^[1] Cardiac imaging before pacemaker implantation is recommended in suspected or documented symptomatic bradycardia to evaluate structural heart disease, determine LV systolic function and diagnose potential causes of conduction disturbance (Class I, Level C); ACC/AHA/HRS 2018 recommends transthoracic echocardiography in newly identified third-degree AV block (COR I, LOE B-NR).^[1][4] ACC/AHA/HRS 2018 also says that in patients with bradycardia, laboratory tests (e.g. thyroid function, Lyme titer, potassium, pH) based on clinical suspicion for a potential underlying cause are reasonable (COR IIa, LOE C-LD).^[4] ESC 2021 adds that multimodality imaging (CMR, CT or PET) should be considered for myocardial tissue characterisation in the diagnosis of specific pathologies associated with conduction abnormalities needing pacemaker implantation, particularly in patients younger than 60 years (Class IIa, Level C).^[1] With transient or reversible causes such as Lyme carditis or drug toxicity, ACC/AHA/HRS 2018 recommends medical therapy and supportive care, including temporary transvenous pacing if necessary, before the need for permanent pacing is determined (COR I, LOE B-NR).^[4]

SAQ 2 (10 marks)

Practice scenario. The man in SAQ 1 is stabilised with a temporary transvenous pacing wire. Thyroid function, Lyme titre, digitalis level, potassium, calcium and pH are normal, and complete AV block persists in sinus rhythm.^[1] Echocardiography shows an LVEF of 45%, and he has no symptoms or signs of heart failure. He is independent and not frail, with no limitation of mobility and no comorbidity limiting life expectancy, and ventricular pacing is expected more than 40% of the time.

1. Does he need a permanent pacemaker? Give the ESC 2021 and ACC/AHA/HRS 2018 positions with their class. (2)^[1][4]
2. Which pacing approach would you discuss with him? Compare ESC 2021, ACC/AHA/HRS 2018, HRS/APHRS/LAHRS 2023 and the 2025 ESC consensus statement on conduction system pacing. (4)^[1][4][5][6]
3. Name two randomised trials relevant to pacing mode in AV block and give their main results. (2)^[10][11]
4. Outline follow-up under ESC 2021, including MRI. (2)^[1]

Model answers — SAQ 2

1. Yes. ESC 2021: pacing is indicated in patients in sinus rhythm with permanent or paroxysmal third-degree AVB, irrespective of symptoms (Class I, Level C), once a reversible cause is excluded.^[1] ACC/AHA/HRS 2018: in acquired third-degree AV block (his ECG a year ago was normal) not attributable to reversible or physiologic causes, permanent pacing is recommended regardless of symptoms (COR I, LOE B-NR), and before implantation the risk of future ventricular arrhythmias and need for an ICD should be assessed (COR I, LOE B-NR).^[4]
2. Use shared decision-making, weighing the best available evidence, individual risks and benefits, the patient's preferences and goals of care (ESC 2021 Class I, Level C).^[1] ESC 2021: in AVB, DDD should be preferred over single-chamber ventricular pacing to avoid pacemaker syndrome and improve quality of life (Class IIa, Level A); ESC 2021 gives this preference when reasonable, i.e. in patients without significant frailty, very advanced age, significant comorbidities limiting life expectancy, or very limited mobility; he is 66, not frail, with no limitation of mobility and no comorbidity limiting life expectancy.^[1] ESC 2021 also says HBP may be considered as an alternative to RV pacing in AVB with LVEF over 40% and more than 20% anticipated ventricular pacing (Class IIb, Level C), and in patients treated with HBP an RV backup lead should be considered in specific situations such as pacemaker dependency, high-grade AVB or infranodal block (Class IIa, Level C); it made no recommendation on LBBAP.^[1] ACC/AHA/HRS 2018: with AV block, a pacing indication, LVEF 36–50% and ventricular pacing expected more than 40% of the time, it is reasonable to choose pacing that maintains physiologic ventricular activation (e.g. CRT or HBP) over RV pacing (COR IIa, LOE B-R, SR: systematic review).^[4] HRS/APHRS/LAHRS 2023: with a pacing indication, LVEF 36–50% and anticipated substantial ventricular pacing, cardiac physiologic pacing is reasonable to reduce the risk of pacing-induced cardiomyopathy (COR 2a; LOE B-R for CRT, B-NR for HBP and LBBAP); its text links an RV pacing burden over 40% with HF hospitalisation in MOST.^[5] The 2026 ESC HF row favouring CRT over RV pacing with high-degree AV block applies to HFrEF, defined there as LVEF below 50% with symptoms and/or signs of HF; he has no symptoms or signs of HF, so it does not apply.^[2] The 2025 ESC consensus statement (a consensus document, not a guideline) states that, in AV block, it may be appropriate to implant CSP with LVEF over 40% and an anticipated ventricular pacing burden over 20%.^[6] The reason for the physiological-pacing options (HBP, CRT or cardiac physiologic pacing, CSP): ESC 2021 reports pacing-induced cardiomyopathy in 10–20% of patients after 2–4 years of RV pacing, associated with an RV pacing burden over 20%, and notes that chronic conventional RV pacing may lead to LV dysfunction and HF in some patients even when AV synchrony is maintained.^[1][5]
3. UKPACE: 2021 patients aged 70 or older having a first pacemaker for high-grade AV block were randomised to single-chamber ventricular or dual-chamber pacing; for the primary outcome, death from all causes, mean annual mortality was 7.2% vs 7.4% (HR 0.96; 95% CI 0.83 to 1.11), with no significant differences in AF, heart failure or the thromboembolic composite (median follow-up 4.6 years for mortality and 3 years for other events).^[10] BLOCK HF: patients with pacing indications for AV block, NYHA class I–III heart failure and LVEF 50% or less were randomised to RV or biventricular pacing; over an average 37 months the primary composite of death from any cause, an urgent care visit for heart failure requiring IV therapy, or a 15% or more increase in LV end-systolic volume index occurred in 55.6% with RV pacing vs 45.8% with biventricular pacing, a significantly lower incidence over time with biventricular pacing (HR 0.74; 95% credible interval 0.60 to 0.90).^[11]
4. ESC 2021: remote device management of pacemakers should be considered to provide earlier detection of clinical problems (e.g. arrhythmias) or technical issues (e.g. lead failure or battery depletion) (Class IIa, Level B), and in patients on remote device management, in-office routine follow-up of single- and dual-chamber pacemakers may be spaced by up to 24 months (Class IIa, Level A).^[1] Remote device management is recommended to reduce in-office follow-ups in pacemaker patients who have difficulty attending in-office visits (e.g. reduced mobility or other commitments) or by patient preference (Class I, Level A); he has no limitation of mobility, so this applies only if attending is difficult for other reasons or he prefers it.^[1] If HBP is used, ESC 2021 advises, because of its higher lead revision rate, follow-up at least once every 6 months or remote monitoring (ensuring that automatic threshold measurements correspond to those measured manually, as this may not be the case and depends on device configuration); if substantial RV pacing cannot be minimised with programming, HRS/APHRS/LAHRS 2023 recommends periodic assessment of ventricular function to detect pacing-induced cardiomyopathy (COR 1, LOE B-NR).^[1][5] MRI can be performed safely following the manufacturer's instructions in MRI-conditional systems (an MRI-conditional generator and lead(s) from the same manufacturer) (Class I, Level A); in non-MRI-conditional systems it should be considered if no alternative imaging is available and there are no epicardial, abandoned or damaged leads or lead adaptors/extenders (Class IIa, Level B).^[1]