Actividad eléctrica del corazón

Question 1

Ondas en el electrocardiograma

Answer 1

• The P wave is produced by atrial depolarization,
• the QRS complex by ventricular depolarization, and
• T wave by ventricular repolarization.
• The U wave is an inconstant finding, believed to be due to slow repolarization of the papillary muscles.

Question 2

Anatomía del Sistema de Conducción Cardiaco

Answer 2

Question 3

Relación entre la conducción de pontencial de acción y ECG

Answer 3

Question 4

Electrocardiograma Derivaciones Unipolar

Answer 4

An additional nine unipolar leads, that is, leads that record the potential difference between an exploring electrode and an indifferent electrode, are commonly used in clinical electrocardiography.

1. There are six unipolar chest leads (precordial leads) designated V1–V6
2. three unipolar limb leads: VR (right arm), VL (left arm), and VF (left foot).
3. Augmented limb leads, designated by the letter a (aVR, aVL, aVF), are generally used.

The augmented limb leads are recordings between one limb and the other two limbs. This increases the size of the potentials by 50% without any change in configuration from the nonaugmented record.

Unipolar leads can also be placed at the tips of catheters and inserted into the esophagus or heart.

Question 5

Características de la derivación aVR en el electrocardiograma normal

Answer 5

The sequence in which the parts of the heart are depolarized and the position of the heart relative to the electrodes are the important considerations in interpreting the configurations of the waves in each lead. The atria are located posteriorly in the chest.

The ventricles form the base and anterior surface of the heart, and the right ventricle is anterolateral to the left.

There is considerable variation in the position of the normal heart, and the position affects the configuration of the electrocardiographic complexes in the various leads.

aVR

• “looks at” the cavities of the ventricles.
• Atrial depolarization, ventricular depolarization, and ventricular repolarization move away from the exploring electrode, and the
• P wave, QRS complex, and T wave are therefore all negative (downward) deflections;

Question 6

Características de aVL y aVF en el electrocardiograma normal

Answer 6

aVL and aVF

• look at the ventricles, and
• the deflections are therefore predominantly positive or biphasic.

Question 7

V1 y V2 en el electrocardiograma normal

Answer 7

V1 and V2

• There is no Q wave in, and
• ventricular depolarization first moves across the midportion of the septum from left to right toward the exploring electrode –>the initial portion of the QRS complex is a small upward deflection
• The wave of excitation then moves down the septum and into the left ventricle away from the electrode –> large S wave.
• Finally, it moves back along the ventricular wall toward the electrode, producing the return to the isoelectric line.

Question 8

Electrocardiograma normal en las derivaciones V4 a V6

Answer 8

Left ventricular leads (V4–V6)

• there may be an initial small Q wave (left to right septal depolarization),
• there is a large R wave (septal and left ventricular depolarization)
• followed in V4 and V5 by a moderate S wave (late depolarization of the ventricular walls moving back toward the AV junction).

Question 9

Electrocardiograma de Asa de His

Answer 9

Se realiza por medio de un cateter

Intervalos:

• PA: conducción entre los nodos sinoatrial y atrioventrucular
• AH: conducción atrioventricular
• HV: condución en el asa de His y sus ramas