ECG

Question 1

waht is a wave?

Answer 1

a deflection, positive or negative, away from the isoelectric line

Question 2

what is a complex?

Answer 2

several waves

Question 3

a segment?

Answer 3

a straight line between waves/complexes

Question 4

Interval?

Answer 4

a segment and a wave

Question 5

Timing on ecg?

Answer 5

Vertical lines

1 small box = 0.04sec

1 large box = 0.2 sec

Question 6

voltage on ecg?

Answer 6

horizontal lines

0.10mV=1small box

Question 8

Normal duration of
PR

QRS

QT

cQT

Answer 8

PR: 120-200 ms (3-5ss)

QRS <=120ms (3ss)

QT <= 0.5 RRinterval

cQT=QT/ (square root from RR interval)

Question 9

Heart rate calculation

Answer 9

No. Of beats in 300 large squares = beats in 1 min

300/(number of large squares between two R waves)

OR (number of QRS) x 6 in the rhythm strip

1500 small squares = 1 minute

1500/(number of small squares between two R waves)

Question 10

a broad T wave means what?

Answer 10

A broader T wave ↔ ↑ heterogeneity of repolarization among cardiac muscle cells →it takes longer (temporal dispersion of refractoriness). This is the substrate for re-entry.

Question 11

QT interval:

what does it measure and what does its prolognation mean?

Answer 11

A long QT interval (a measure of the duration of repolarization) may identify the patient at risk for ventricular arrhythmias and sudden death.

The QT prolongation of hypocalcemia has somewhat less risk. This is the only cause of QT prolongation where the duration of the T wave is not prolonged—a normal T wave just occurs later.

Question 12

Upward or downward QRS complexes and concordant T waves in which leads?

Answer 12

In the young:

Upward & concordant: **I, II, III, aVF, V3-V6 **

DOwnward & concordant: aVR, V1, V2

In older adults, T waves are upward in V2 and sometimes V1 despite the fact that QRS are downward.

Question 13

Physiological Q waves represent what?

Normal parameters?

Answer 13

Physiological Q waves represent the upwards depolarisation of the septum (in II, II, aVF)

In V6, V5 leads, the Q wave represents Lefto to Right septal depolarisation.

Normally, q wave is <0.04s (<1ss wide), no deeper than 25% of subsequent R wave.

Question 14

Left Bundle Branch distribution and actions

Answer 14

Left bundle branch (LBB) branches into:

1. Left anterior fascicle (LAF).LAF depolarises ant & lat walls of LV.
2. Left posterior fascicle (LPF).
   LPF depolarises the post & inf surfaces of LV simultaneously.
3. Septal branch

Question 15

Normal cardiac axis

Answer 15

Normal cardiac axis – leads I,II, II have positive QRS complexes.

Normal cardiac axis - -30˚ to 90˚, if the axis lies beyond aVL (-30˚) → left axis deviation (LAD).

If beyond aVF (90˚) →right axis deviation (RAD).

Question 16

Left Axis Deviation due to & appearance:

Answer 16

due to LAF bkock

Left anterior descending artery pathology (ischemia, infarction),

LVH,

cardiomyopathy.

As the axis moves towords the left, III begins to delelop s wave, even further, lead II will also develop an s wave. Lead I retains a stron r wave At the limit of normality, the axis lies at a VL = lead II is isoelectic (r wave= s wave).
In the LAD: negative leads II & III, strongly positive – lead I

Question 17

Right axis deviation due to

Answer 17

due to LPF block usualy, diffuse ischemia/infarction, cardiomyopathy. Local ischemia rarely ahs a significant effect because of extensive anastomosis of blood supply.

Loss of a large part of LV myocardium due to MI (left lateral infarction), shifts the axis to the right and vice versa.

Question 18

QRS complexes in LAD & RAD

Answer 18

In both LAD and RAD – QRS complexes are wider (but still within normal range) due to a slight delay of depolarisation in the affected area.

Question 19

DIagnostics of LVH

Answer 19

Sokolow-Lyon: S wave in V1 + R wave in V5 or V6 (whichever higher) ≥3.5mV

OR R wave in V5 or V6 > 2.3mV

Cornell: R in aVL + S in V3 > ♂2.8mV or ♀2.0mV

Question 20

RVH diagnostics

Answer 20

R wave > 7ss in lead V1

or

R:S ratio >1 in V1 suggests RVH.

Question 21

In what lead is P wave normally negative?

Answer 21

aVR

Question 22

Normal P wave measurments

Answer 22

Normal Pwave is

<2.5ss (0.11s)

and

<2.5mm amplitude.

Question 23

RA enlargement

Answer 23

RA enlarges downward and to the right → amplitude of P wave↑ (>2.5mm (2.5 ss) in II, III, AVF) in inferior leads, but the width is still normal.

Question 24

LA enlargement

Answer 24

LA enlargement →prolongation of P wave (> 2.5ss). Also, increased asynchrony results in notched P wave (two peaks = P mitrale). If the peaks are >0.05s (1ss) apart, it is indicative of LA enlargement. May produce a negative deflection after a P wave in V1 (>1ss in width and depth)