Most ECGs are recorded at standard settings of 25 mm/sec paper speed and 10mm = 1 mV. At these standard settings, the rectangular calibration signal at the start of the trace should be 5 small squares wide and 10 small squares high. If the calibration signal is not this size, the ECG may have been recorded at non-standard settings and all of the usual rules for calculating rate, segments, intervals and heights may not apply.See also: Rate
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This ECG is from a female in her 60s presented with chest pressure for 1 hour. She had a history of hypertension and smoking. She described the pain as a "buffalo sitting on my chest". She also described a "weird" sensation in her jaw for 1 hour prior to arrival, associated with lightheadedness and diaphoresis.
This ECG is from a young man presented after a stab wound to the chest. Rapid ED diagnosis of cardiac penetrating trauma was made by ED ultrasound, and the patient went to the OR and had a wound to the right atrium repaired. There was no laceration of any coronary vessel. He did well. This ECG was recorded at day 3 because of tachycardia.