Sinus rythm
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sinus rhythm ECG definition normal sinus rhythm American Heart Association
Sinus rhythm is the heart’s normal electrical rhythm. The impulse starts in the sinoatrial (SA) node, the heart’s natural pacemaker, then travels through the atria and ventricles in an organized pattern.
On an ECG, sinus rhythm generally means:
- A P wave before every QRS complex
- Each P wave has a similar shape
- Regular R-R intervals
- P waves are usually upright in lead II
- Normal resting rate in adults is commonly 60-100 beats/min. A sinus-origin rhythm below this is called sinus bradycardia; above it is sinus tachycardia.
So, if an ECG report says “normal sinus rhythm”, it usually indicates a normal heart rhythm.
sinus tachycardia
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sinus tachycardia causes management guideline American Heart Association
Sinus tachycardia is a fast but normally conducted heart rhythm that still begins in the sinoatrial (SA) node. In adults, it usually means a resting heart rate over 100 beats/min.
ECG features
- Regular rhythm
- Normal-looking P wave before every QRS complex
- Rate rises and falls gradually, unlike many re-entry tachycardias that start and stop abruptly
Common causes
- Exercise, stress, anxiety, pain
- Fever, dehydration, anemia
- Caffeine, nicotine, alcohol, stimulant drugs, some medications
- Hyperthyroidism
- Infection, low oxygen, blood loss, pulmonary embolism, or heart disease
It is often a normal response to a trigger. The main treatment is to identify and treat that cause, rather than simply suppress the heart rate. This is consistent with Harrison's approach to sinus tachycardia and NCBI clinical guidance.
Seek urgent medical assessment if a fast resting pulse occurs with chest pain, breathlessness, fainting, confusion, severe dizziness, or low blood pressure, or if it is persistent without an obvious cause.
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