Management of Type 2 Diabetes Patient with Sinus Bradycardia, Intermittent Mobitz I AV Block, and Dizziness
Before considering permanent pacing, you must systematically exclude reversible causes—particularly medications, sleep apnea, and metabolic derangements—because Mobitz I (Wenckebach) AV block is typically benign and rarely requires pacing unless symptoms are directly attributable to bradycardia after reversible factors are addressed. 1
Initial Evaluation: Establish Symptom-Rhythm Correlation
Document temporal correlation between dizziness and bradycardia using ambulatory monitoring (24–48 hour Holter, event recorder, or mobile cardiac telemetry based on symptom frequency) to confirm that symptoms occur during bradycardic episodes rather than other causes. 2
Obtain a 12-lead ECG during symptomatic episodes if possible to confirm the rhythm disturbance and determine QRS morphology (narrow vs. wide escape rhythm). 1
Assess hemodynamic stability by checking for syncope, presyncope, heart failure symptoms, chest pain, hypotension, altered mental status, or dyspnea—these indicate urgent intervention may be needed. 3
Exclude Reversible Causes (Mandatory Before Pacing Decision)
Medication Review
Systematically review all AV nodal blocking agents: beta-blockers, non-dihydropyridine calcium channel blockers (verapamil, diltiazem), digoxin, and antiarrhythmic drugs. 2, 4
Consider BRASH syndrome (Bradycardia, Renal failure, AV-nodal blockade, Shock, Hyperkalemia) in this diabetic patient—check renal function, potassium, and assess for synergistic toxicity between AV nodal blockers and renal insufficiency. 5
If the patient is on metformin and develops acute kidney injury, this can precipitate a vicious cycle of hyperkalemia and worsening bradycardia requiring urgent dialysis and cessation of AV nodal blockers. 5
Sleep Apnea Screening
Screen for obstructive sleep apnea in any patient with obesity, daytime tiredness, and symptomatic sinus bradycardia or SA block—this is a critical reversible cause that can eliminate the need for pacing. 6
If sleep apnea is diagnosed, initiate nCPAP therapy first; pacemaker should only be considered if nCPAP is not tolerated or fails to reduce bradyarrhythmia. 6
Laboratory Evaluation
Check thyroid function (TSH, free T4), electrolytes (potassium, magnesium, calcium), renal function (creatinine, eGFR), and consider Lyme serology if epidemiologically appropriate. 1
Evaluate for acute myocardial infarction with troponin and ECG, as AV block in the setting of acute MI may be transient. 1
Management Algorithm Based on Findings
If Reversible Cause Identified
Treat the underlying condition first with medical therapy and supportive care, including temporary transvenous pacing if necessary, before determining need for permanent pacing. 1
Do not implant a permanent pacemaker if AV block completely resolves after treatment of the reversible cause—this is classified as harmful (Class III). 1
If Symptoms Persist After Addressing Reversible Causes
For Symptomatic Sinus Bradycardia
Permanent pacing is indicated (Class I) if symptoms are directly attributable to sinus node dysfunction after reversible causes are excluded. 1
Atrial-based pacing is recommended over single-chamber ventricular pacing in patients with intact AV conduction to avoid pacemaker syndrome. 1
Dual-chamber or single-chamber atrial pacing is recommended for symptomatic sinus node dysfunction with intact AV conduction and no conduction abnormalities. 1
For Mobitz I (Wenckebach) AV Block Specifically
Mobitz I AV block at the AV nodal level typically does not require permanent pacing unless the patient has documented symptomatic bradycardia directly attributable to the block after reversible causes are excluded. 1
Permanent pacing is reasonable (Class IIa) if the patient is on chronic stable doses of medically necessary antiarrhythmic or beta-blocker therapy (e.g., for heart failure or atrial fibrillation) and develops symptomatic second-degree AV block. 1
Consider a trial of oral theophylline (Class IIb) in patients with symptoms likely attributable to sinus node dysfunction to increase heart rate, improve symptoms, and help predict the potential benefit of permanent pacing. 1, 2
Acute Management if Hemodynamically Unstable
For AV-nodal level block (narrow QRS escape): Give atropine 0.5–1 mg IV bolus, repeat every 3–5 minutes up to a total of 3 mg; avoid doses <0.5 mg as they may paradoxically worsen block. 1, 3
Atropine is ineffective for infranodal blocks (wide QRS escape)—do not delay pacing in these patients. 1, 3
Initiate transcutaneous pacing immediately for hemodynamically unstable patients or those unresponsive to atropine, serving as a bridge to transvenous pacing. 1, 3
Temporary transvenous pacing is reasonable for persistent hemodynamically unstable bradycardia refractory to medical therapy until a permanent pacemaker is placed or the bradycardia resolves. 1
Critical Pitfalls to Avoid
Do not implant a pacemaker for asymptomatic sinus bradycardia or Mobitz I AV block—this is Class III (harmful) unless other high-risk features are present. 1
Do not miss sleep apnea as a reversible cause in obese patients with daytime tiredness—nCPAP can eliminate the need for pacing. 6
Do not overlook BRASH syndrome in diabetic patients on AV nodal blockers with renal insufficiency—this requires urgent dialysis and cessation of offending medications, not pacing. 5
Do not proceed to permanent pacing if symptoms do not correlate temporally with documented bradycardia on ambulatory monitoring. 2
Do not use single-chamber ventricular pacing in patients with intact AV conduction and VA conduction, as this increases risk of pacemaker syndrome. 7