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An R wave follows as an upward deflection, and the S wave is any downward deflection after the R wave. The T wave follows the S wave, and in some cases, an additional U wave follows the T wave. To measure the QRS interval start at the end of the PR interval (or beginning of the Q wave) to the end of the S wave.
The dead tissue is surrounded by a zone of potentially reversible ischemia that progresses to become a full-thickness transmural infarct. [76] [79] The initial "wave" of infarction can take place over 3–4 hours. [73] [76] These changes are seen on gross pathology and cannot be predicted by the presence or absence of Q waves on an ECG. [78]
The cycle also correlates to key electrocardiogram tracings: the T wave (which indicates ventricular diastole); the P wave (atrial systole); and the QRS 'spikes' complex (ventricular systole)—all shown as color purple-in-black segments. [1] [2] The Cardiac Cycle: Valve Positions, Blood Flow, and ECG The parts of a QRS complex and adjacent ...
Rule 9: There is no Q wave or only a small q (<0.04 seconds in width) in I, II and V2 to V6. Rule 10: The T wave is upright in I II and V2 to V6. The end of the T wave should not drop below the isoelectric baseline. Rule 11: Does the deepest S wave in V1 plus the tallest R wave in V5 or V6 equal >35 mm? Rule 12: Is there an Epsilon wave?
Respiration gives rise to waves in heart rate mediated primarily via the PSNS, and it is thought that the lag in the baroreceptor feedback loop may give rise to 10 second waves in heart rate (associated with Mayer waves of blood pressure), but this remains controversial. [citation needed]
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Note that only the cardiac troponins are used clinically for myocardial infarction as creatine kinase adds little value in diagnosing MI while adding to system cost. [17] [18] [19] The diagnosis of myocardial infarction requires two out of three components (history, ECG, and enzymes).
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