Compare conditions

Put any two — or three — conditions side by side, adult or pediatric, to spot the look-alike differences fast, row by row.

Slow heartbeat

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In one line

·The heart beats too slowly to pump enough blood for the body's needs.

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Normal physiology

·The SA node (the heart's natural pacemaker at the top of the right atrium) fires an electrical signal 60–100 times per minute. The signal travels to the AV node (the relay station between the upper and lower chambers), pauses briefly, then spreads through the bundle of His and Purkinje fibers to make the ventricles (lower pumping chambers) squeeze and push blood out to the body.

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What goes wrong

·Usually one broken part of the heart's electrical system explains all the symptoms together.

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Hallmark signs

·Feeling tired and weak
·Feeling dizzy or lightheaded
·Fainting or feeling like you're about to faint
·Shortness of breath
·Chest pain or pressure
·Confusion or trouble thinking clearly
·Can't do your usual activities without getting exhausted
·Low blood pressure

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Red flags · escalate now

·Fainting or nearly fainting—your brain isn't getting enough blood, and you're at risk of dangerous pauses in your heartbeat.
·Chest pain or sudden trouble breathing—may mean a heart attack, heart failure, or fluid backing up into your lungs.
·Confusion or trouble staying awake—means your brain is starved for oxygen and needs emergency care.
·Blood pressure below 90 on the top number, with cold skin, weak pulse, or little urine—your body is going into shock and organs may start failing.
·New complete heart block or advanced second-degree heart block on the ECG (the electrical tracing of your heart)—the electrical signals between your heart's upper and lower chambers are failing, and your heart could stop.

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Workup

·12-lead electrocardiogram (ECG)
·Serum potassium and magnesium
·Thyroid-stimulating hormone (TSH) and free T4
·Medication review (especially beta-blockers, calcium channel blockers, digoxin, and antiarrhythmic drugs)
·High-sensitivity troponin I or troponin T
·Continuous heart monitoring (telemetry)
·Serum creatinine and blood urea nitrogen (BUN)
·Digoxin level (if the patient is taking digoxin)

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Treatment

·Atropine 1 mg IV push, can repeat every 3 to 5 minutes up to a total of 3 mg
·Transcutaneous pacing (TCP) or transvenous temporary pacemaker wire
·Stop or reduce beta-blockers, calcium channel blockers (diltiazem, verapamil), digoxin, and antiarrhythmic drugs (amiodarone, sotalol)
·Correct high potassium with calcium gluconate or calcium chloride IV, insulin with dextrose IV, sodium bicarbonate IV if acidotic, and sodium polystyrene sulfonate (Kayexalate) or patiromer by mouth, or hemodialysis; replace low magnesium with magnesium sulfate IV; treat hypothyroidism with levothyroxine by mouth
·Epinephrine infusion 2 to 10 mcg per minute IV or dopamine infusion 5 to 20 mcg per kg per minute IV if atropine fails and pacing is not immediately available
·Permanent pacemaker implantation for symptomatic sinus node dysfunction (sick sinus syndrome), Mobitz type II second-degree AV block, third-degree (complete) AV block, or symptomatic a slow heart rate (bradycardia) when necessary heart-slowing medicines cannot be stopped
·Treat acute heart attack (myocardial infarction) (heart attack) if present: aspirin 162 to 325 mg chewed immediately, anticoagulation with heparin or enoxaparin, and emergency coronary revascularization with percutaneous coronary intervention (PCI, cardiac catheterization with stent) or coronary artery bypass graft (CABG) surgery

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NCLEX trap

·Never give drugs that slow the heart when the heart is already beating too slowly and causing symptoms. Beta-blockers (drugs like metoprolol that block adrenaline and slow the heart) and calcium-channel blockers (drugs like diltiazem that block calcium and slow the heart's electrical signals) will push the heart rate even lower, drop blood pressure, and starve the brain and other organs of oxygen. Instead, STOP any drugs that slow the heart and get ready to speed it up with atropine (a drug that blocks the vagus nerve, the body's main brake on the heart, and lets the heart beat faster), pacing (using electrical pulses to make the heart beat), or epinephrine (a hormone and drug that makes the heart beat faster and squeeze harder).
·A slow heart rate that causes dizziness, fainting, shortness of breath, or confusion is an emergency, even in athletes. These symptoms mean the body is not getting enough blood and oxygen. Treat right away — do not wait. A resting heart rate under 60 can be normal for a fit person who feels fine, but if the person feels sick or passes out, it is NOT normal and the heart is not pumping enough blood to meet the body's needs.
·Atropine works only if the sinoatrial node (the heart's natural pacemaker, a cluster of special cells in the right atrium that fires to start each heartbeat) is firing too slowly, or if the atrioventricular node (the relay station between the top chambers and bottom chambers) is slowing signals because of too much vagus nerve activity (the body's main brake on the heart) or certain drugs. If the problem is a physical block in the electrical pathway below the AV node — in the bundle of His or bundle branches (the wiring that carries the heartbeat signal through the thick bottom pumping chambers, the ventricles) — atropine will not help and may even make things worse by speeding the top chambers while the bottom chambers stay slow, creating an unstable rhythm. Read the ECG (a tracing of the heart's electrical activity) to figure out WHERE the block is, then match your treatment to that specific problem, not just to the slow heart rate number.
·In a slow heart rate (bradycardia), the patient's symptoms are the real emergency. Stabilize the patient first: make sure the airway is open, breathing is adequate, and blood is circulating. Then figure out what is causing the slow heart rate. The heart rate is just a number on the monitor — the patient's symptoms (dizziness, confusion, chest pain, shortness of breath) and blood pressure tell you whether the slow heart rate is causing harm right now.
·A transplanted heart is denervated (it has no vagus nerve connection because the nerves were cut during surgery). Atropine works by blocking the vagus nerve, so it will NOT work in a transplanted heart. Use transcutaneous pacing (electrical pacing through sticky pads on the chest that deliver timed shocks to make the heart beat) or an epinephrine infusion (a continuous drip of a drug that speeds the heart and makes it squeeze harder) instead. Always review the patient's history — it changes which treatments will work.
·A slow heart rate can come from three different places: (1) sinus a slow heart rate (bradycardia) (the SA node is firing too slowly), (2) AV nodal block (the electrical signal is blocked at the AV node, the junction between the atria and ventricles), or (3) infranodal block (the block is below the AV node in the bundle of His, bundle branches, or Purkinje fibers — the wiring that spreads the electrical signal through the ventricles). You must look at the 12-lead ECG, check the patient's medications, measure electrolytes (potassium, magnesium, and calcium — minerals in the blood that help the heart's electrical system work), and ask about the patient's history to figure out the actual site of the problem. Do not assume the cause based on the heart rate alone.

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