TsÊ Loop in the Elucidation of “Left Ventricular Strain” Pattern in Hypertension  SURAJ P. AHUJA, M.B., B.S., J.A. LEWIS, M.D., F.C.C.P.  Diseases of the Chest  Volume 49, Issue 4, Pages 405-411 (April 1966) DOI: 10.1378/chest.49.4.405 Copyright © 1966 The American College of Chest Physicians Terms and Conditions

FIGURE 1 Ischemic ST segment depression in L1, aVL and V6, coveplane morphology of the ST segment in V4 and inverted T-waves in the corresponding leads (upper portion) in an untreated hypertensive patient revert to normal within one month after effective control of blood pressure (lower portion). All electrocardiographic tracings are recorded on normal standardization. Diseases of the Chest 1966 49, 405-411DOI: (10.1378/chest.49.4.405) Copyright © 1966 The American College of Chest Physicians Terms and Conditions

FIGURE 2 Vectorcardiogram before treatment of the patient referred to in Fig. 1, showing initial and terminal parts of the QRS loop (direction of inscription indicated by interrupted arrows), P loop, and ST-T loop (direction of inscription indicated by solid arrows). T-loop was only partially photographed in the horizontal and frontal planes for more precise appraisal of its rotation. QRS loop is inscribed in a counterclockwise manner in all three projections. See text for further details. (H=horizontal; F=frontal; LS=left sagittal). Diseases of the Chest 1966 49, 405-411DOI: (10.1378/chest.49.4.405) Copyright © 1966 The American College of Chest Physicians Terms and Conditions

FIGURE 3 Thin double lines represent part of the QRS loop, and the thick single line, the T-loop. Direction of inscription is indicated by the arrows. Normal: The mean axes of the QRS and T loops are very close to each other—normal QRS-T angle—, and the T loop is inscribed concordant to QRS rotation in all the three planes. Left ventricular strain Grades—1.: QRS-T angle widens; the T loop inscription is concordant in all projections; 2.: T loop is oriented diametrically opposite to the QRS mean axis, but retains concordant inscription; 3.: In addition to the very wide QRS-T angle, the horizontal T-loop is discordantly rotated. The frontal and left sagittal T-loops are still concordant in their inscription. 4.: T-loop becomes discordantly inscribed in the frontal plane, too; 5.: T-loop is discordantly oriented and inscribed in all planes. (Modified from Amer. Heart 57:552, 1959). Diseases of the Chest 1966 49, 405-411DOI: (10.1378/chest.49.4.405) Copyright © 1966 The American College of Chest Physicians Terms and Conditions

FIGURE 4 Vectorcardiogram of the hypertensive patient (referred to in Figs. 1 and 2) following normalization of blood pressure. The QRS loop is written in a counterclockwise manner in the horizontal and left sagittal projections and clockwise in the frontal plane. The TsÊ loop is concordantly inscribed. The QRS-T angle is within normal range in all planes. Diseases of the Chest 1966 49, 405-411DOI: (10.1378/chest.49.4.405) Copyright © 1966 The American College of Chest Physicians Terms and Conditions

FIGURE 5 A case of subacute pericarditis showing inverted T-waves in II, III, aVF and V6. FIGURE 6: Vectorcardiogram in a case of subacute pericarditis (referred to in Fig. 5). The QRS loop is inscribed in a counterclockwise direction in the horizontal and left sagittal planes and clockwise in the frontal projection. The TsÊ loop is discordantly oriented and inscribed in all planes. Diseases of the Chest 1966 49, 405-411DOI: (10.1378/chest.49.4.405) Copyright © 1966 The American College of Chest Physicians Terms and Conditions

FIGURE 7 Electrocardiogram showing cupped ST segments in II, III, aVF and V6 and shortened QTc interval—characteristic of “digitalis effect.” FIGURE 8: Vectorcardiogram (corresponding to the electrocardiogram in Fig. 7), in digitalis effect. QRS loop is inscribed in a counterclockwise manner in the horizontal and left sagittal planes and in a figure of 8 pattern in the frontal projection with predominant clockwise rotation. TsÊ loop is located diametrically opposite to the mean QRS axis, but is inscribed concordantly in all planes. Terminal conduction delay in the QRS loop is felt to be on the basis of ischemic heart disease. Diseases of the Chest 1966 49, 405-411DOI: (10.1378/chest.49.4.405) Copyright © 1966 The American College of Chest Physicians Terms and Conditions

FIGURE 9 Vectorcardiogram in a hypertensive patient following restoration of normal blood pressure. QRS and T loops are concordantly inscribed—counterclockwise in the horizontal and left sagittal planes and clockwise in the frontal projection. Terminal conduction delay noted in the QRS loop had been present prior to treatment. Diseases of the Chest 1966 49, 405-411DOI: (10.1378/chest.49.4.405) Copyright © 1966 The American College of Chest Physicians Terms and Conditions