Dizziness at 98 bpm in Phase II Cardiac Rehab
Ms. R is a 62-year-old woman starting phase II cardiac rehabilitation three weeks after an NSTEMI treated with PCI to the circumflex artery. Her resting ECG shows sinus rhythm at 62, PR 218 ms, QRS 138 ms with a left bundle branch pattern, and left axis deviation; there are no acute ST changes. During the intake 6-minute walk test, the monitor shows transient 2:1 AV block when her heart rate reaches 98, and she reports brief dizziness that resolves when she stops. Medications include metoprolol succinate 100 mg daily and atorvastatin. She had one syncopal episode last year that was never investigated. Her cardiologist's note states "cleared for exercise, no restrictions." She is eager to start treadmill walking today.
1. How do you interpret the combination of conduction findings and symptoms, and does the cardiologist's clearance settle your decision?
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The findings are not incidental.
- PR 218 ms is first-degree AV block; QRS 138 ms with LBBB pattern and left axis indicates conduction disease in the His-Purkinje system (bundle branch disease).
- New 2:1 AV block that appears at 98 bpm during exertion, with dizziness reproduced at the same moment, is the key finding. Exertional AV block in the presence of bundle branch block suggests infranodal disease, which can progress abruptly to complete heart block. It is not a benign vagal phenomenon, which typically appears at rest or with recovery.
- The unexplained syncope last year fits a possible bradyarrhythmic mechanism and has never been evaluated.
Does clearance settle it? No. Clearance addresses coronary anatomy and infarct stability. It does not certify the conduction system, and it was written without knowledge of today's monitor finding. A therapist who proceeds because the note says "no restrictions" is deferring to a document rather than to the patient in front of them.
Conclusion: defer supervised aerobic exercise at rates that provoke block; this is a same-day conversation with cardiology/electrophysiology, not a next-visit one.
2. What do you do in the next 30 minutes, and what do you document and tell the patient?
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Immediate actions:
- Keep her seated and monitored; do not start treadmill walking or any graded aerobic task.
- Repeat vital signs, obtain a rhythm strip of the block if the monitor can print or store it, and capture a 12-lead if available.
- Call cardiology/EP the same day, describe the rate threshold (98 bpm), the symptom, and the resting conduction abnormalities; request guidance and an urgent evaluation.
- If she becomes symptomatic with sustained bradycardia or hypotension while in your care, activate emergency response per facility protocol.
- Offer safe low-demand activity only if approved: breathing exercises, seated flexibility, light active ROM well below the provoking rate, with continuous monitoring.
Documentation: rhythm strips and time stamps; HR at onset and resolution; symptoms and duration; resting ECG intervals; medications; that aerobic exercise was deferred and why; who was contacted, when, and the response; education given, including not to exercise unsupervised at home until evaluated.
To the patient, in plain language: "Your heart's electrical signal slows down when you walk fast enough, and that is what makes you dizzy. That is separate from your stent being fine. We are not going to push through it. Your cardiologist needs to see this today, and we will design a plan after that. Do not walk for exercise at home until you hear from us."
3. She returns five weeks later after dual-chamber pacemaker implantation. How does your exercise prescription and monitoring change?
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What changes:
- Rate no longer reflects effort reliably. Her paced rate may be fixed, rate-responsive, or limited by the programmed upper tracking rate (commonly 130–150 bpm). Use RPE (target 11–13), talk test, workload in METs or watts, and dyspnea ratings as primary anchors; treat heart rate as a safety boundary, not a target.
- Programmed limits matter. Ask for the settings: lower rate, upper tracking/sensor rate, rate-response mode. Exercise that demands a rate above the upper limit will cause a plateau, not a physiologic ceiling; work is still fine if symptoms allow.
- Arm precautions. Avoid heavy upper-extremity resistance and extreme shoulder elevation/pectoral stretch for roughly 4–6 weeks post-implant per implanting team, to protect lead integrity. Light ROM and walking are fine.
- Monitor for recurrence. If dizziness returns, capture the rhythm and check for rate drops, loss of tracking, or pacemaker-mediated issues; report rather than adjust activity alone.
- Resume graded aerobic training at low-to-moderate intensity with a warm-up long enough to let rate response engage, progress by tolerance, and continue ECG-monitored sessions initially.
Reasoning: the pacemaker treats the conduction risk; it does not restore normal chronotropic physiology, so prescription must shift from heart rate to effort-based anchors.