What does the Q wave represent in MI?

Technically, a Q wave indicates that the net direction of early ventricular depolarization (QRS) electrical forces projects toward the negative pole of the lead axis in question. Although prominent Q waves are a characteristic finding in myocardial infarction, they can also be seen in a number of noninfarct settings.

When does Q wave appear in MI?

Q wave myocardial infarction refers to myocardial infarctions that in a Q wave forming on the 12-lead ECG once the infarction is completed.

What happens to the Q wave during an MI?

Pathologic Q waves are a sign of previous myocardial infarction. They are the result of absence of electrical activity. A myocardial infarction can be thought of as an elecrical ‘hole’ as scar tissue is electrically dead and therefore results in pathologic Q waves.

What is a septal Q wave?

Abstract. Background: Small Q waves in the left lateral leads are termed septal q waves, and their response to exercise has been reported to be a marker of septal ischemia in coronary artery disease.

Are Q waves bad?

The Q wave is a small negative deflection that precedes the R wave. Small Q waves (<0.03 seconds in duration) are a normal finding in all leads except V1 through V3, where they are always pathologic.

Why is the Q wave a downward deflection?

As septal depolarization moves from left to right, the depolarization vector is directed towards the – electrode of lead II (RA), and therefore a negative-going deflection (Q-wave) is produced.

How long do Q waves last?

For MI, Q waves last longer than 0.04 second, and depth exceeds one-third of the R wave (inferior wall MI). For inferior wall MI, differentiate it from right ventricular hypertrophy by axis deviation.

How long do Q waves take to develop?

Q waves may develop within one to two hours of the onset of symptoms of acute myocardial infarction, though often they take 12 hours and occasionally up to 24 hours to appear. The presence of pathological Q waves, however, does not necessarily indicate a completed infarct.

Where is the Q wave?

The Q wave is the first downward deflection after the P wave and the first element in the QRS complex. When the first deflection of the QRS complex is upright, then no Q wave is present. The normal individual will have a small Q wave in many, but not all, ECG leads.

Are septal Q waves normal?

Normal septal q waves are characteristically narrow and of low amplitude. As a rule, septal q waves are less than 0.04 sec in duration. A Q wave is generally abnormal if its duration is 0.04 sec or more in lead I, all three inferior leads (II, III, aVF), or leads V3 to V6.

What happens during the Q wave?

This is known as a Q wave and represents depolarisation in the septum. Whilst the electrical stimulus passes through the bundle of His, and before it separates down the two bundle branches, it starts to depolarise the septum from left to right.

Are Q waves ever normal?

QRS. The Q wave is a small negative deflection that precedes the R wave. Small Q waves (<0.03 seconds in duration) are a normal finding in all leads except V1 through V3, where they are always pathologic. Q waves of any size may be normal in leads III and aVR.

What do Q waves mean on an EKG?

The ekg has waves with amplitude and direction. A q wave reflects a lack of electrical force in a certain direction. This lack of force has some correlation when a change in pattern with a loss of muscle as is seen in heart damage like a heart attack. Old infarct.

What do Q waves mean?

medical Definition of Q wave. : the short initial downward stroke of the QRS complex in an electrocardiogram formed during the beginning of ventricular depolarization .

What does a significant Q wave indicate?

Q waves are “significant” if they are greater than 1 box in width (longer than 0.04 msec) OR are larger than 1/4 of the R wave. Significant Q waves indicate either myocardial infarction or obstructive septal hypertrophy (IHSS). The first upward deflection of the QRS is called the R wave.

What is an ECG pattern?

A grid pattern is typical of ECG paper, and a series of lines cross one another to break the spaces down to squares generally 0.04 inches (one millimeter) wide. Darker lines, usually red in color, cross to block off squares that are five boxes across and five high.