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25/01/1432 ELECTROCARDIOGRAM "ECG“ "ECG“ Physiology Department Cairo University الرحيم يم ن ر الرحمن بسم ﷲ ر ب م 2010--2011 2010 3 41- 2 1 Regarding the causes of the ECG waves all the following are correct EXCEPT: a- P wave by atrial depolarization a depolarization. b- QRS complex by ventricular depolarization. c- T wave by ventricular repolarization. d- U wave by papillary muscle depolarization. 1 40- In the fundamental rules of the ECG all the following are right EXCEP: a- It is a biphasic record of myocardial action potential fluctuations. b- Deflection record occurs only during complete depolarization or repolarization. c- +ve wave occurs when depolarizing current approaches the +ve terminal electrode of the meter. d- -ve wave happens when repolarizing current approaches the +ve terminal electrode. 25/01/1432 42- The causes of the ECG “intervals”: a- PR by AV nodal conduction. LF arm RT arm b- ST by atrial repolarization. c- QT by ventricular depolarization and ventricular repolarization. d- All of the above. RT leg LF leg + Terminal Electrode Einthoven's triangle: - A triangle with the heart at its center. - obtained from the three standard limb leads record. - Zero potential is obtained if the 3 electrodes are connected to a common indifferent electrode. 2 + Terminal Electrode + Terminal Electrode 25/01/1432 1 2 3 aVR + Terminal Electrode aVL + Terminal Electrode aVF + Terminal Electrode + Terminal Electrode LI V6(+ve) Last Depolarization -ve to +ve current 3 1st V1(+ve) 25/01/1432 + Terminal Electrode LI 1st Repolarization +ve to –ve current Different QRS complex nomenclatures “Growing R" 2 1 1 1 2 4 V3(+ve) Last 25/01/1432 2 1 1 2 1 V4(+ve) 45- Axis of the heart is: 44- The voltage of the ECG: a- Mean instantaneous vector of QRS complexes in a- Is normal summation of QRS complexes in vertical plane. b Normally bN ll from-30 f 30 to t +60. +60 b Normally bN ll equals l <1.5 <1 5 mV. V c- Deviated to left side in full term pregnant woman. c- Is low in an individual having body mass d- Deviated to right side in long slender person (e.g., +80). 5 standard limb leads. index (BMI) 35. d- All of the above. 25/01/1432 47- The configuration of QRS complex in normal ECG: a- Depends only on the direction of depolarizing current. b- Is mainly positive in right ventricular surface pattern. c- Exhibits growing R in chest leads. 46- The P-wave of normal ECG: a- Has voltage and duration nearly equal 2.5 × 2.5 mm. b Is bI upright i ht in i aVR. VR c- Represents right atrial depolarization in its second half. d- Coincides with atrial systole. d- Is positive in aVR. 48- As regards Q wave all the following are 49- In normal ECG: a- The average duration of QT interval is 0.50 sec. b- The ST segment is an isoelectric line. c- The T wave is rounded and symmetrical. d- The height of the T wave is > 10 mm in chest leads. correct EXCEPT: a- Represents septal depolarization from left to right in V5. b Its depth is not more than 1/4 its corresponding bR. c- Its duration is not more than 0.04 sec. d- Is deep and wide in recent myocardial infarction. 6