Sick Sinus Syndrome (Tachy-Brady syndrome)
📖 About
- Also called Sick Sinus Syndrome (SSS) or Tachy-Brady Syndrome.
- Results from dysfunction or damage of the sinus node, the heart’s natural pacemaker.
- Leads to alternating episodes of bradyarrhythmias 🐢 and supraventricular tachyarrhythmias ⚡.
- More common in elderly patients due to sinus node fibrosis.
📈 ECG Features
- Sinus bradycardia (HR <60 bpm) 🐢
- Sinus node arrest or pause (absent/delayed P waves ⏸️)
- Episodes of supraventricular tachyarrhythmias (SVT, AF, flutter) ⚡
- Tachy-Brady alternation → paroxysmal atrial fibrillation/flutter followed by sinus pauses
- QRS rate may be <60 or >100 bpm depending on phase
⚠️ Causes
- Degenerative fibrosis of the sinus node (most common, age-related 👴)
- Ischaemic heart disease / myocardial infarction ❤️
- Infiltrative disease (amyloidosis, sarcoidosis) 🧬
- Cardiac surgery or trauma (esp. post-atrial surgery)
- Drugs: beta-blockers, digoxin, CCBs 💊
- Hypothyroidism 🦋
🧪 Investigations
- 12-lead ECG (look for sinus bradycardia, pauses, tachy-brady episodes)
- Holter or event monitoring 🎧 to capture intermittent episodes
- Bloods: U&E, LFTs, TFTs (thyroid especially), FBC
- Consider echocardiogram to assess structural disease
🛠️ Management
- Asymptomatic → may not require specific treatment ✅
- Review medications that worsen bradycardia (BBs, CCBs, digoxin) 💊
- Pacing: Symptomatic bradycardia, sinus pauses, or syncope → permanent pacemaker 💓
- Tachyarrhythmias: Use rate-controlling drugs carefully (after pacing if brady risk high)
- Atrial fibrillation/flutter: Anticoagulation as per CHA₂DS₂-VASc 🩸
💡 Clinical Pearl:
“Tachy-Brady Syndrome” = alternation between fast SVTs (AF/flutter) and long sinus pauses 🐢⚡.
These patients often require a pacemaker first → then rate-control or anti-arrhythmics.
📚 Case Example
👩 A 74-year-old woman presents with dizziness and two syncopal episodes.
ECG: Sinus bradycardia at 42 bpm 🐢. Holter shows paroxysmal AF ⚡ alternating with long sinus pauses.
✅ Diagnosis: Sinus Node Disease (Tachy-Brady Syndrome).
🛠️ Management: Permanent pacemaker 💓 + anticoagulation for AF 🩸.
