Wednesday, 16 November 2016

Pericarditis





Acute pericarditis is a type of pericarditis (inflammation of the sac surrounding the heart, the pericardium) usually lasting less than 6 weeks. It is by far the most common condition affecting the pericardium.

Typical ECG changes in acute pericarditis includes:
  • stage 1 - diffuse, positive, ST elevations with reciprocal ST depression in aVR and V1. Elevation of PR segment in aVR and depression of PR in other leads especially left heart V5, V6 leads indicates atrial injury.
  • stage 2 - normalization of ST and PR deviations
  • stage 3 - diffuse T wave inversions (may not be present in all patients)
  • stage 4 - ECG becomes normal OR T waves may be indefinitely inverted
The two most common clinical conditions where ECG findings may mimic pericarditis are acute myocardial infarction (AMI) and generalized early repolarization.

Parasystole



Parasystole is a kind of arrhythmia caused by the presence and function of a secondary pacemaker in the heart, which works in parallel with the SA node. Parasystolic pacemakers are protected from depolarization by the SA node by some kind of entrance block. This block can be complete or incomplete.
Parasystolic pacemakers can exist in both the atrium or the ventricle. Atrial parasystolia are characterized by narrow QRS complexes.

There are two forms of ventricular parasystole, fixed parasystole and modulated parasystole. Fixed ventricular parasystole occurs when an ectopic pacemaker is protected by entrance block, and thus its activity is completely independent from the sinus pacemaker activity. Hence, the ectopic pacemaker is expected to fire at a fixed rate. Therefore, on ECG, the coupling intervals of the manifest ectopic beats will wander through the basic cycle of the sinus rhythm. Accordingly, the traditional electrocardiographic criteria used to recognize the fixed form of parasystole are:
  • the presence of variable coupling intervals of the manifest ectopic beats;
  • inter-ectopic intervals that are simple multiples of a common denominator;
  • fusion beats.

Monday, 14 November 2016

P Wave Asystole


Another form of Asystole you may encounter is called P wave asystole or Ventricular Asystole. The features are the same as traditional Asystole, but with one exception, there will be P waves present in the ECG tracing. The patient is clinically dead. The patient will not survive with just atrial depolarization and will require CPR.

Asystole



Asystole, also known as flatline, is a state of no electrical activity from the heart and therefore no blood flow. It results in cardiac arrest. Survival rates in a cardiac arrest patient with asystole are much lower than a patient with a rhythm amenable to defibrillation; asystole is itself not a "shockable" rhythm.



Ventricular Standstill



Ventricular standstill is the absence of any ventricular activity for more than a few seconds. There may be atrial activity as evidenced by P waves in which case complete heart block is blocking all impulses from reaching the ventricles and the backup or subsidiary pacemaker has failed, or there may be an absence of atrial and ventricular activity.


Agonal Rhythm


An agonal heart rhythm is a variant of asystole with a heart rate is less than 20 bpm, without P waves and with wide, bizarre QRS complexes seen on the electrocardiogram. Clinically, an agonal rhythm is regarded as asystole and should be treated equivalently, with cardiopulmonary resuscitation. As in asystole, the prognosis for a patient presenting with this rhythm is very poor.

3rd Degree AV Block



Third-degree atrioventricular block (AV block), also known as complete heart block, is a medical condition in which the impulse generated in the sinoatrial node (SA node) in the atrium of the heart does not propagate to the ventricles.

Because the impulse is blocked, an accessory pacemaker in the lower chambers will typically activate the ventricles. This is known as an escape rhythm. Since this accessory pacemaker also activates independently of the impulse generated at the SA node, two independent rhythms can be noted on the electrocardiogram (ECG).
  • The P waves with a regular P-to-P interval (in other words, a sinus rhythm) represent the first rhythm.
  • The QRS complexes with a regular R-to-R interval represent the second rhythm. The PR interval will be variable, as the hallmark of complete heart block is lack of any apparent relationship between P waves and QRS complexes.
Patients with third-degree AV block typically experience severe bradycardia (an abnormally low measured heart rate), hypotension, and at times, hemodynamic instability.