What is the initial management for an elderly patient with a history of cerebral vascular accident (CVA) infarct, diabetes, presenting with easy fatigability and bipedal edema, hypotension, severe bradycardia, normal oxygen saturation, mild tachypnea, third-degree atrioventricular (AV) block, impaired renal function, and normal potassium levels?

Initial Management of Third-Degree AV Block in an Elderly Diabetic Patient Post-CVA

This patient requires immediate temporary cardiac pacing given the complete heart block with severe symptomatic bradycardia (HR 39) and hypotension (BP 100/70), followed by preparation for permanent pacemaker implantation. 1

Immediate Interventions (First 5-10 Minutes)

Stabilization and Monitoring

• Establish continuous cardiac monitoring and secure IV access immediately 1
• Administer supplemental oxygen if hypoxemic (though O2 sat is 99% in this case) 1
• Obtain 12-lead ECG to confirm complete heart block and assess QRS morphology (narrow vs wide escape rhythm determines level of block) 1
• Assess for signs of poor perfusion: altered mental status, chest pain, acute heart failure, or worsening hypotension 1

Pharmacologic Bridge Therapy

• Administer atropine 0.5-1.0 mg IV bolus as first-line therapy for symptomatic bradycardia 1
  • May repeat every 3-5 minutes up to maximum total dose of 3 mg 1
  • Critical caveat: Atropine is contraindicated in third-degree AV block at the His-Purkinje level (wide QRS escape rhythm), as it will not improve ventricular rate and may worsen hemodynamics 1
  • In this diabetic patient with prior CVA, use cautiously as tachycardia may increase myocardial oxygen demand 1

Definitive Management: Temporary Pacing

Class I Indication for Temporary Pacing

Complete (third-degree) heart block is a Class I indication for temporary transvenous pacing 1

Pacing Strategy

• Prepare for immediate temporary transvenous pacemaker insertion 1
• Consider transcutaneous (external) pacing as bridge until transvenous access established 1
• Use AV sequential pacing when possible to preserve atrial contribution to cardiac output, especially important given this patient's likely compromised ventricular function (evidenced by bipedal edema suggesting heart failure) 1

Critical Assessment Points

Evaluate for Reversible Causes

• Review medication list: Beta-blockers, calcium channel blockers, digoxin, amiodarone can cause AV block 1
• Check electrolytes beyond the reported K=4.5: magnesium, calcium 1
• Assess for acute myocardial infarction: Check troponin and serial ECGs, as MI is a reversible cause 1
• Consider Lyme disease or infiltrative processes (sarcoidosis, amyloidosis) in appropriate clinical context 2

Renal Function Considerations

The elevated creatinine (1.9) requires dose adjustment of renally-cleared medications and careful monitoring if contrast studies needed 1

Preparation for Permanent Pacemaker

Class I Indication

Permanent pacemaker implantation is indicated for acquired third-degree AV block that is not due to reversible causes 1, 2

Pre-Implantation Workup

• Echocardiography to assess: left ventricular function, structural heart disease, and determine if cardiac resynchronization therapy (CRT) indicated 2
• Consider coronary angiography if acute coronary syndrome suspected, though this can be deferred if patient stabilizes 3

Special Considerations in This Patient

Diabetes-Specific Concerns

• Diabetic patients have 1.40 times higher risk of AV block and conduction abnormalities compared to non-diabetics 4
• Assess for cardiac autonomic neuropathy: Check for orthostatic hypotension, resting tachycardia, or abnormal heart rate variability 1
• Optimize glycemic control as poor control associated with worse cardiovascular outcomes 1

Post-CVA Considerations

• Diabetic patients post-CVA have worse prognosis with slower recovery and greater disability 5
• Intracranial stenosis is 3.13 times more common in diabetics, increasing CVA risk 6
• Maintain adequate cerebral perfusion pressure: The current BP of 100/70 with HR 39 may be insufficient for adequate cerebral blood flow in a patient with prior stroke 5

Heart Failure Management

The bipedal edema suggests volume overload, but diuresis should be deferred until after pacing established to avoid worsening hypotension 1

Common Pitfalls to Avoid

• Do not give atropine doses <0.5 mg, as paradoxical bradycardia may occur 1
• Do not delay temporary pacing while waiting for atropine response in complete heart block 1
• Do not use atropine for wide-complex escape rhythms (infranodal block), as it is ineffective and classified as Class III 1
• Avoid nephrotoxic contrast if possible given elevated creatinine, but do not delay necessary coronary angiography if acute MI suspected 1
• Do not attribute all symptoms to the AV block without ruling out acute MI, pulmonary embolism, or other acute processes 1

Disposition

Admit to cardiac intensive care unit for continuous monitoring, temporary pacing, and preparation for permanent pacemaker implantation within 24-48 hours 1