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A standard 12-lead ECG report (an electrocardiograph) shows a 2.5 second tracing of each of the twelve leads. The tracings are most commonly arranged in a grid of four columns and three rows. The first column is the limb leads (I, II, and III), the second column is the augmented limb leads (aVR, aVL, and aVF), and the last two columns are the ...
The use of additional ECG leads like right-sided leads V3R and V4R and posterior leads V7, V8, and V9 may improve sensitivity for right ventricular and posterior myocardial infarction. In spite of these limitations, the 12 lead ECG stands at the center of risk stratification for the patient with suspected acute myocardial infarction.
The standard 12 lead ECG does not directly examine the right ventricle, and is relatively poor at examining the posterior basal and lateral walls of the left ventricle. In particular, acute myocardial infarction in the distribution of the circumflex artery is likely to produce a nondiagnostic ECG. [ 10 ]
In humans, for an ECG to be described as showing a sinus rhythm, the shape of the P wave in each of the 12 standard ECG leads should be consistent with a "typical P vector" of +50° to +80°. [2] This means that the P wave should be: always positive in lead I, lead II, and aVF; always negative in lead aVR
Lead II — This axis goes from the right arm to the left leg, with the negative electrode on the shoulder and the positive one on the leg. This results in a +60 degree angle of orientation. [4] = Lead III — This axis goes from the left shoulder (negative electrode) to the right or left leg (positive electrode). This results in a +120 degree ...
Since pacemaker correction of the third-degree block requires full-time pacing of the ventricles, a potential side effect is pacemaker syndrome, and may necessitate the use of a biventricular pacemaker, which has an additional 3rd lead placed in a vein in the left ventricle, providing more coordinated pacing of both ventricles.
An ST elevation is considered significant if the vertical distance inside the ECG trace and the baseline at a point 0.04 seconds after the J-point is at least 0.1 mV (usually representing 1 mm or 1 small square) in a limb lead or 0.2 mV (2 mm or 2 small squares) in a precordial lead. [2] The baseline is either the PR interval or the TP interval ...
A 12 lead ECG showing sinus tachycardia. Sinus tachycardia is usually apparent on an ECG, but if the heart rate is above 140 bpm the P wave may be difficult to distinguish from the previous T wave and one may confuse it with a paroxysmal supraventricular tachycardia or atrial flutter with a 2:1 block.