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HEART SPECIALISTS IN H S R LAYOUT BANGALORE A systematic description of ECGs The following eight short steps will enable most ECGs to be described correctly: 1 Check the paper speed and calibration markers. 2 Measure or estimate the heart rate. 3 Estimate the rhythm. 4 Look for P waves. 5 Measure the PR interval. 6 Examine the QRS complex. 7 Check the ST segment. 8 Measure the T wave. ECG interpretation should always be as restrained as practicable, taking into account the clinical context where known and comparison with previous tracings where possible. The possibility of Prinzmetal’s electrocardiographic heart disease must always be borne in mind—that is, do not assume that an abnormal ECG always means heart disease.2 Paper speed and calibration markers The standard paper speed is 25 mm/second. This means that 1 mm (small square) = 0.04 seconds and 5 mm (large square) = 0.20 seconds. Provided that the grid is shown, this gives the time scale regardless of the actual image magnification used. Voltage is measured on the vertical axis: 10 mm = 1 mV, as shown in the calibration artefact Leads are often described in groups that correspond approximately to the area of the heart they represent. n Leads 1 and aVL are (high) lateral leads. n Leads 2, 3 and aVF are inferior leads. n Leads 1, 2, 3, aVL, aVF and aVR are collectively called limb or frontal plane leads. Leads 1, 2 and 3 are standard limb leads, while leads aVL, aVF and aVR are augmented limb leads. n Leads V1 and V2 are anteroseptal leads. n Leads V3 and V4 are anterior leads. n Leads V5 and V6 are anterolateral leads. n Leads V1–V6 are collectively called chest, precordial or horizontal plane leads. 3• AN OVERVIEW OF CLINICAL ELECTROCARDIOGRAPHY 49 Heart rate By definition, sinus tachycardia is a heart rate ≥ 100/minute and sinus bradycardia is a heart rate ≤ 50/minute.3 To calculate the heart rate from the ECG, the R-R interval in mm can be divided into 1500. For example, an R-R interval of 20 mm gives a rate of 75/minute and an R-R interval of 15 mm gives a rate of 100. Similarly, large 5 mm squares can be divided into 300; thus three squares give a rate of 100/minute. In regular rhythms, any two congruous points of the P-QRS-T sequence can be used to estimate the rate. An ECG ruler has a scale that enables rapid rate measurement and calculation of other intervals. With practice, the rate can be estimated at a glance. Rhythm Begin by looking for P waves. They are best seen in lead 2 (L2) (which is calculated electrocardiographically as the arithmetic sum of leads 1 and 3), aVR (where everything including the P waves
HEART SPEACIALIST IN BANGALORE HYPERTENTION By definition, sinus tachycardia is a heart rate ≥ 100/minute and sinus bradycardia is a heart rate ≤ 50/minute.3 To calculate the heart rate from the ECG, the R-R interval in mm can be divided into 1500. For example, an R-R interval of 20 mm gives a rate of 75/minute and an R-R interval of 15 mm gives a rate of 100. Similarly, large 5 mm squares can be divided into 300; thus three squares give a rate of 100/minute. In regular rhythms, any two congruous points of the P-QRS-T sequence can be used to estimate the rate. An ECG ruler has a scale that enables rapid rate measurement and calculation of other intervals. With practice, the rate can be estimated at a glance.
THE BEST CARDIOLOGISTS IN YELAHANKA A systematic description of ECGs The following eight short steps will enable most ECGs to be described correctly: 1 Check the paper speed and calibration markers. 2 Measure or estimate the heart rate. 3 Estimate the rhythm. 4 Look for P waves. 5 Measure the PR interval. 6 Examine the QRS complex. 7 Check the ST segment. 8 Measure the T wave. ECG interpretation should always be as restrained as practicable, taking into account the clinical context where known and comparison with previous tracings where possible. The possibility of Prinzmetal’s electrocardiographic heart disease must always be borne in mind—that is, do not assume that an abnormal ECG always means heart disease.2.
PAPULAR CARDIOLOGISTS IN HEBBALA ECG interpretation: points to remember 1 ECG reports should be short and based on clinical information where possible. 2 Check that the patient’s name is on the ECG and that the paper speed and calibration markers are correct. 3 Measure or estimate the heart rate—3 large squares = 100/minute. 4 Establish the rhythm. Look for P waves (best seen in L2). Are the P waves followed by QRS complexes? Look for anomalously conducted or ectopic beats. 5 Measure the intervals: PR, QRS duration and QT interval (for the latter, consult tables, but normal is less than 50% of the RR interval). 6 If the QRS complex is wide (> 3 small squares) consider the possibilities: LBBB, RBBB, WPW or ventricular rhythm or beats. If the pattern is of LBBB, there is no need in most cases to attempt further interpretation. 7 Estimate the QRS axis. In LAD, L1 and aVF diverge and L2 is predominantly negative. In RAD, L1 and aVF converge, while L2 matters little. Indeterminate axis is diagnosed when all six frontal leads are (more or less) equiphasic. 8 Check whether the criteria for LAHB or LAFB have been met. 9 Look for pathological Q waves. In general these are longer than 0.04 seconds and are more than 25% of the size of the following R wave.
A risk factor is a demographic characteristic associated with an increased risk of ischaemic heart disease when other variables have been controlled. The presence of a risk factor in an individual increases his or her relative risk of a coronary event (angina, infarction or death). The absolute risk of a coronary event depends on the individual’s total number of risk factors and theirseverity (total risk). Important coronary risk factors are shown in Table 1.1. Risk assessment charts have been developed to estimate a patient’s cardiac risk over a number of years using easily identified risk factors. There are charts for different populations. The charts can be used to predict cardiovascular events or mortality (as in the NHF chart in Fig 1.1 on p. 4) or cardiac risk (systematic coronary risk evaluation system or SCORE charts). These charts can be very helpful in deciding when intervention to reduce risk is warranted; for example, when anti-hypertensive treatment should be commenced for a patient with mild blood pressure elevation. Risk factor reduction involves assessing the presence, severity and importance of risk factors for a
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