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POPULAR CARDIOLOGISTS IN H S R LAYOUT Ventricular tachycardia Ventricular tachycardia is defined as three or more ventricular ectopic beats at a rate over 100/minute. It is said to be sustained if it lasts more than 30 seconds. Most broad-complex tachycardias are ventricular (rather than supraventricular with aberrant conduction). The diagnosis of VT is greatly strengthened if there is a history of myocardial infarction or cardiac failure but, oddly enough, the patient’s haemodynamics are of no help. A number of criteria have evolved over the years to help ascertain the diagnosis of VT over aberrancy. These include: evidence of AV dissociation—P waves can be seen unrelated to the QRS complexes (they are usually visible only at relatively slow VT rates) the presence of supraventricular capture or fusion beats visible retrograde conduction with 2:1 block (P waves visible following every second complex) the presence of monophasic R, qR or QR patterns in V1, provided a septal infarction has not modified a RBBB a taller left rabbit ear in RR' or qRR' complexes in V1 n QS complexes in V1 with a slow S descent and sharp upstroke—the opposite of LBBB—or a broad small primary R wave in rS morphology (the Rosenbaum pattern) RAD in the frontal plane with LBBB-like QRS complexes
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.
THE BEST HEART SPECIALIST S IN YELAHANKA ST segment There are two aspects to report: depression and elevation. Depression The ST segment is said to be abnormal if it slopes down 1 mm or more from the J point—the end of the QRS complex (downsloping depression)—or is depressed 1 mm or more horizontally (plane depression). Depression of the J point itself may be normal, especially during exercise, but this upsloping ST depression should return to the isoelectric line within 0.08 seconds. The isoelectric line is defined as the PR or TP segment of the ECG . ST depression may be due to ischaemia, the effect of digoxin, hypertrophy and so on. Elevation ST elevation of up to 3 mm may be normal in V leads (especially the right), and up to 1 mm may be normal in limb leads. This ST elevation is called early repolarisation syndrome or pattern. Otherwise ST elevation may mean an acute myocardial infarction where it is said to represent a current of injury. Pericarditis also causes ST elevation but unlike infarction is usually associated with concave upwards elevation. hypertrophy and conduction defects like LBBB can be associated with ST elevation in leads where the QRS is mostly negative. T waves The T wave is always inverted in lead aVR and often in L3 and V1–V2, and in aVL if the R wave is less than 5 mm tall. Inversion and flattening are common and non-specific findings. Deep (> 5 mm) symmetrical and persistent (days to weeks) inversion is consistent with infarction; broad, ‘giant’ inversion may follow syncope from any cause including cerebrovascular accidents. Like the ST segment, the T wave tends to be directed opposite to the main QRS deflection in conduction defects (e.g. LBBB), VEBs or ventricular hypertrophy (where it is described as secondary ST/T changes or strain pattern). Tall peaked T waves are most often seen as a reciprocal change to inferior or posterior infarcts. They are classically seen in patients with hyperkalaemia. Broader large T waves are seen in early (‘hyperacute’) infarction and sometimes in cerebrovascular accidents. While not diagnostic by themselves (T waves never are), when they are associated with modest ST elevation (especially in V3) and reciprocal depression in the inferior leads, they indicate infarction or ischaemia. When these changes evolve over time they are even more specific for infarction A U wave may be prominent in patients with hypokalaemia, LVH and bradycardia. Isolated
CARDIAC CENTERS IN YELAHANKA NEW TOWN BANGALORE ST segment There are two aspects to report: depression and elevation. Depression The ST segment is said to be abnormal if it slopes down 1 mm or more from the J point—the end of the QRS complex (downsloping depression)—or is depressed 1 mm or more horizontally (plane depression). Depression of the J point itself may be normal, especially during exercise, but this upsloping ST depression should return to the isoelectric line within 0.08 seconds. The isoelectric line is defined as the PR or TP segment of the ECG . ST depression may be due to ischaemia, the effect of digoxin, hypertrophy and so on. Elevation ST elevation of up to 3 mm may be normal in V leads (especially the right), and up to 1 mm may be normal in limb leads. This ST elevation is called early repolarisation syndrome or pattern. Otherwise ST elevation may mean an acute myocardial infarction where it is said to represent a current of injury. Pericarditis also causes ST elevation but unlike infarction is usually associated with concave upwards elevation. hypertrophy and conduction defects like LBBB can be associated with ST elevation in leads where the QRS is mostly negative. T waves The T wave is always inverted in lead aVR and often in L3 and V1–V2, and in aVL if the R wave is less than 5 mm tall. Inversion and flattening are common and non-specific findings. Deep (> 5 mm) symmetrical and persistent (days to weeks) inversion is consistent with infarction; broad, ‘giant’ inversion may follow syncope from any cause including cerebrovascular accidents. Like the ST segment, the T wave tends to be directed opposite to the main QRS deflection in conduction defects (e.g. LBBB), VEBs or ventricular hypertrophy (where it is described as secondary ST/T changes or strain pattern). Tall peaked T waves are most often seen as a reciprocal change to inferior or posterior infarcts. They are classically seen in patients with hyperkalaemia. Broader large T waves are seen in early (‘hyperacute’) infarction and sometimes in cerebrovascular accidents. While not diagnostic by themselves (T waves never are), when they are associated with modest ST elevation (especially in V3) and reciprocal depression in the inferior leads, they indicate infarction or ischaemia. When these changes evolve over time they are even more specific for infarction . A U wave may be prominent in patients with hypokalaemia, LVH and bradycardia. Isolated U inversion is a specific but insensitive sign of coronary disease. 54 PRACTICAL CARDIOLOGY ECG reports Reports should be short and stereotyped, with the description clearly separated from the comment. It is a good general strategy to under-report, especially for a beginner. It is generally wiser to state ‘inferior Q waves noted’ or ‘non-specific ST/T changes’ than to indulge in speculation on possible or probable infarction or ischaemia. ECG labels tend to have serious employment and insurance implications. On the other hand, specific questions on the request form must be addressed, since they constitute the reason for taking the ECG in the first place.
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
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