ECG to continue….

Interval changes assessment

PR (PQ) interval• Normally .12 s - .20 s

• (that is 3 – 5 mm of horizontal distance)

• Shorter (e.g.) in preexcitation syndromes

• Longer (e.g.) in AV block of first degree

• Dependent of the frequency

• For 60 beats / s is around 0.45 s

QT interval

Preexcitation syndromes

Accessory signal pathwayOrientation of QRS complex vector depends on the direction of propagation of the signal

Sy Wolff-Parkinson-White has “delta” waveSy Lown-Ganong-Levin

(without “delta” wave)Risk of supraventricular

paroxysmal tachycardia

type A type B

Reentry tachyarrythmiasReentry in Wolff-Parkinson-White’s Syndrome

Accessory pathway Ectopic atrial extrasystole

tachycardia

Short PRwave

AV block

1-st degree: Long PR inteval

2-nd degree type one

type two

3-rd degree: No connection between atria and ventriculi

AV block of 2-nd degree

Wenkebach’s periods

(Mobitz II)

AV block of 3-rd degree

Other causes of interval changes

• Short PR interval preexcitation sy,sympathetic act., hypoK,AV nodal rhythms from the beginning of it

• Long PR interval AV block 1-st degree parasympathetic act.,

hyperK,IHD, medicaments (e.g. beta blockers)

• Short QT interval Digitalis,hyperCa (hyperK – tall pointing T wave)

• Long QT hypertension, after MI

hypoCa, (hypoK– U wave),

Congenital (risk of sudden death)

QRS – left ventricular overload

• Sokolow’s index: R in (V5 or V6) + S inV1 > 35mmAttention young slim individuals (heart as a voltage source is closer to the chest leads – bigger voltage on the leads without hypertrophy)

physiological Left heart hypertrophy

QRS – right ventricular overload

Vertical electrical axis (> 100°)in V1: R >= 7mm or qR (volume overload)in avR: r > 4 mm in V6: R smaller/equal S (volume overload)

Physiological Pressure overload Physiological Volume overload

QRS - right BBB

• Causes: Dilatation and/or overload of right heart, MI,

sometimes “physiological”

• QRS > 0,11 s

• If complete, then R’(r’) wave is bigger then R(r ) in V1

• Repolarization changes

QRS – left BBB

• Causes: IHD, hypertension,

cardiomyopathy,

valvular disease,

unknown

• QRS >0,11s (with complete block)

• Discordant T! and discordant dinivelization of ST

QRS – Q wave myocardial infarction

• In the Q-wave MI, there is necrosis throughout the cardiac wall, while in the non-Q wave, necrosis affects the endocardial zone only.

• Pathological Q-waveAppears in the first 0,04 s of QRSAppears in the leads where there

should be no Q or overlays the normal R (r) (e.g. in V1 to V5) – absence of the R-wave

Deeper then 2mm (6mm in III) Q > 0,25 R for I, II, avL, (avF) Q > 0,15 R forV1 to V6

QRS – Q wave MI

• There is no Q-wave in the beginning, but so-called “Pardee’s” wave (elevation of ST+ negative T)

• We imagine the (left) heart as pyramid to describe the MI location.

• Anterior • Septal (right)• Lateral (left)• Inferior (down side at the apex)

and it’s posterior extension (close to the base of the pyramid)

Combination of BBB and MI

QRS – serious embolism, fibrosis, hydropericardium

Beware – some changes are result of lead displacement