What is the significance of placing the leads in intercostal spaces for ECG's.?

Answer 1

mostly it helps to standardize placement of leads so that an EKG can be compared to other EKGs and give the same information

Answer 2

The 6 chest leads are placed between the ribs in the intercostal space as the electrical activity is able to be detected through muscle easier than bone. The location of the chest leads has changed over time and the present locations are terribly out of date. The electrocardiogram has not advanced in 50 years despite tremendous technological advance and there are every year or so a few articles with suggestions for more chest leads which would provide a much more thorough recording of the heart's electrical activity.

Answer 3

An ECG is constructed by measuring electrical potential between various points of the body using a galvanometer. Leads I, II and III are measured over the limbs: I is from the right to the left arm, II is from the right arm to the left leg and III is from the left arm to the left leg. From this, the imaginary point V is constructed, which is located centrally in the chest above the heart. The other nine leads are derived from potential between this point and the three limb leads (aVR, aVL and aVF) and the six precordial leads (V1-6). Leads Readings

Therefore, there are twelve leads in total. Each, by their nature, record information from particular parts of the heart:

The inferior leads (leads II, III and aVF) look at electrical activity from the vantage point of the inferior region (wall) of the heart. This is the apex of the left ventricle.
The lateral leads (I, aVL, V5 and V6) look at the electrical activity from the vantage point of the lateral wall of the heart, which is the lateral wall of the left ventricle.
The anterior leads, V1 through V6, and represent the anterior wall of the heart, or the frontal wall of the left ventricle.
aVR is rarely used for diagnostic information, but indicates if the ECG leads were placed correctly on the patient.
Understanding the usual and abnormal directions, or vectors, of depolarization and repolarization yields important diagnostic information. The right ventricle has very little muscle mass. It leaves only a small imprint on the ECG, making it more difficult to diagnose than changes in the left ventricle.

The leads measure the average electrical activity generated by the summation of the action potentials of the heart at a particular moment in time. For instance, during normal atrial systole, the summation of the electrical activity produces an electrical vector that is directed from the SA node towards the AV node, and spreads from the right atrium to the left atrium (since the SA node resides in the right atrium). This turns into the P wave on the EKG, which is upright in II, III, and aVF (since the general electrical activity is going towards those leads), and inverted in aVR (since it is going away from that lead).

If the precordal leads are placed over a rib instead of on the appropriate intercostal space, there is interferance from the bone in the ability to detect the electrical activity. Although this may result in only a momentary delay in detection, it can effect the final measurements. In the case of V1-V3, dealing with portions of right ventrical, there is only a small electrical imprint to begin with, and anything which interfered with detection of the imprint could result in the likelyhood of missing a problem in that area- and it is already a difficult area to diagnose changes in without adding interferance from a rib.

Answer 4

The leads need to be placed in the intercostal spaces because they need to be in the less obstructing view of the heart to pick up the best rhythm (rather than over rib).