appunti del dott. Claudio Italiano
cfr anche i link correlati al tema su : Aritmie2 cuore e diabete ecg ecg2 atrial fibrillation fibrillazione ventricolare T waves of ischemia at the electrocardiogram Ecg and heart attack, the classic signs infarto
After writing these things, I will not let myself be seen for a while by my prof.Peppino Oreto!
Each cardiac cell is equipped with electric charges, due to the presence of ions, inside K + and outside Na +; however, the presence of proteins with negative electrical charges in the cytoplasm determines an electronegative environment inside the cell; if we want to measure this potential with two electrodes between inside and outside the cell, the value will be -100 mV (rest potential). Following a stimulation, however, this electric potential changes and describing a characteristic profile passes to positive (depolarization); this phenomenon depends on the passage of Na + inside the cell and, subsequently, with the escape of K +, the cell returns to the value of the resting potential. However, a set of cells that are invested by this phenomenon generate a wave of depolarization, which can be represented as a dipole, arranged by convention with the positive sign forward, ie in the sense of the depolarization current and with the negative tail.
At this point, if we want to detect such a depolarization activity that involves the myocardium, on the ECG trace, it is represented by a positive deflection if the electrode that explores this dipole is placed in front, that is, if it "sees" such dipole approach him, if, on the other hand, the dipole moves away, it will be negative.
The repolarization phase, in which the cells, by effect of the membrane pumps, resume the electronegative charge inside, is represented as a wave of repolarization or recovery phase or T wave. In the final analysis a cardiac cycle is given by P wave of atrial electric activity, linked to the contraction of the atria, and a QRS complex, where Q must always be very small, R is the positive deflection and S the negative deflection, which constitute the activity of the ventricles; at this point a section S and T follows, and the wave T, then a pause; the ST segment is of considerable importance for the interpretation of the ECG, because it expresses the state of the coronary and oxygenation of the myocardium, understood as blood flow; in the case of an acute infarct, this trait is generally very overlapped with respect to the isoelectric line on which it normally lies, or, in the posterior infarcts, under-segmented on V1 and V2. Finally, it is recalled that a state of ventricular hypertrophy is accompanied by signs of overload, that is ST under-stratified and sometimes T negative with asymmetric branches with R in V5 and V6 of high voltage.
ECG: Example of derivations D1-D2-D3
ECG: AVF isodifasica because the electric axis is horizontal and coincides with zero
Observe in our ECG:
- is aVL positive? Yes, so the dipole depolarization looks towards the aVL electrode, on the left that is positive.
- is aVF positive? Is D1 positive? aVF, no, because it is the most isodifhasic, D1 yes, so the axis coincides with zero, also because the highest R is in D1 which is the derivation placed at 0 ° on the front axis.
- Is PR regular? Yes, PR is almost, we said; The QRS is spread over 3 small squares? No, so there is no branch block or hemiblock, nor does it have enlarged configurations as for extrasystoles or branch block where the ST segment is negative. Neither there are QS waves in D3 and D2 or R-R1 appearance complexes as for BBD (right branch block) in V1 and V2; neither in V5 or V6 (see the piece of tracing with the derivations from V1 to V6 in the column, one above the other, they allow to study the heart slice by slice, starting from the right up to the left ventricle (V5 -V6).
In the case that a QRS complex is of size over 0, 2 sec, it means that there is a block between the conduction of the impulses between the atria and the ventricles; we know, in fact, that there is a specific myocardial tissue called a node of the SENO where the pulses are automatically made, or pacemakers: from here through specific ways the signal passes to the atrioventricular node or AV, to be sent to the right and left bundles of His. Well, the PR trait is an expression of the atrio-> ventricular conduction of the depolarization wave, which if it goes beyond the established time means that the tissue has problems in conduction: ATRIOVENTRICULAR BLOCK (see the arrhythmias on this site).
Another thing to be observed in the ECG is the presence of the wave P and if it is positive or negative, that is, if the signal starts from the atriums, or if the electrical signal leads to the other halls by another path marker . Another thing to observe are the QRS complexes, because if there is a block of the downstream conduction, ie in the right branch (BBD) or in the left branch (BBS) of the beam of His the QRS will be spread out and of odd shape, to M , with cusps R and R1, ie as 2 peaks, because the depolarization of the ventricles will be asynchronously:
Nel caso del blocco di branca sinistra, l’aspetto sarà di un QRS slargato come con due cuspidi unite da un tratto a concavità verso l'alto. Tale aspetto occorrerà valutarlo in V1 e V2 per il BBD, e nelle derivazioni toraciche V5 e V6 per un BBS.
(vedi per approfondire cfr > ecg 2 ecg altri segni)
Hypertrophy of the ventricles
HYPERTROPHY Left Ventricle = when measuring the S wave in V1 and the R wave in V5, the measurement will be greater than 35 mm + T inverted
HYPERTROPHY Right Ventricle = high voltage R waves in V1-V2-V3-V4.
HYPERTROPHY LEFT Atrium = P-diffusive wave as a horizontal S;
HYPERTROPHY right Atrium = high voltage P wave.
IMBALANCES WITH ELECTROLYTES
Hyperkalaemia: T-pointed wave or QRS slarged
Hypopotassiemia: flat T wave
Hypercalcemia: short QT
hypocalcemia: QT: long;
In the course of pericardial effusion, ST is flattened and suprasliveled with a concave tract and ST goes over the isoelectric line.
Long and under-lined QT, P uncinata; wave U after T, as bending to U. Traced to "roller coaster" in case of overdose.
IN THE READING OF THE ECG,
RHYTHM, FREQUENCY, CONDUCT, STATUS OF THE QRS AND AXIS, HYPERTROPHY, INFARCTION.