Ventricular asystole (standstill)

Ventricular asystole (standstill)

ECG characteristics

· Atrial rhythm : usually indiscernible

· Ventricular rhythm : none

· Atrial rate : usually indiscernible

· Ventricular rate : none

· P wave : may be present in ventricular asystole , may be

absent in atrial asystole

· QRS complex : absent , occasionally a wide QRS complex

(Agonal rhythm) is present

· T wave : absent

· Other : waveform is nearly flat line when asystole

affects atrium and ventricles

Possible causes

· Any condition which prevents adequate blood flow i.e. pulmonary embolism, air embolism, haemorrhage

· Cardiac tamponade

· Myocardial rupture

· Hypoxemia

· Heart failure

· Coronary artery disease

· Cardiomyopathy

· Rheumatic heart disease

· Ventricular arrhythmia

· AV block

· Severe acidosis

· Electrolyte imbalance i.e. Hypokalaemia, hyperkalaemia

· Digoxin toxicity

· Pulseless electrical activity

· Electric shock

· Blunt or penetrating heart trauma

· Cocaine overdose

Treatment

· Emergency sternotomy

· CPR

· Transthoracic pacing

· Drug therapy (Adrenaline and Atropine)

· Consider insertion of temporary pacing wire or pacing swan

Twelve-lead ECG

All patients admitted for cardiac surgical procedures and major thoracic procedures require a preoperative 12-lead baseline ECG. It is repeated again following cardiac surgical procedures on the operative day (within the first 15 minutes) and on the fifth postoperative day. Additional ECG may be requested for patients with evidence of intraoperative myocardial damage. A standard ECG consists of three bipolar limb leads (1, 11, 111), three unipolar limb leads ( aVL, aVF, aVR) and six unipolar chest leads (V1-V6).The ECG is analysed in terms of rhythm, ischaemic changes including territory (new and old), axis deviation and intraventricular conduction defects.

Determining the heart’s rate and rhythm

· On an ECG strip the P wave (atrial depolarisation), QRS complex (ventricular depolarisation) and T wave (repolarisation) represents one heartbeat.

· Determine if the rhythm is regular or irregular (Place blank strip of paper below the strip and mark the distance two or more consecutive R waves. If the interval between the marks corresponds to the interval between the R waves, then the rhythm is regular)

· To estimate the rate, count the number of R waves on a six-second strip and multiply by 10.

Analysing cardiac conduction

· Is there a P wave before every QRS complex?

· Are all the P wave same shape?

· Is the PR interval .12 - .20 seconds?

· If the PR interval > .20 seconds there is a delay in conduction (1° block)?

· Is there a prolongation of the PR interval until a QRS complex is missing (2° block)?

· Is there no relationship between P waves and QRS complexes (3° block)?

· Measure the QRS complexes. Are they < .12 seconds and all look the same? (Wide bizarre complexes may signal premature ventricular contractions or ventricular tachycardia)

· Measure the QT interval, which should be between .36 and .44 seconds. A prolonged QT could indicate drug toxicity or electrolyte imbalance.

· Look at the ST segment. Does it coincide with the isoelectric line? If the segment appears below or above the line it could symbolise epicardial or endocardial injury caused by myocardial ischaemia or a myocardial infarction

You’ll know that the patient is in normal sinus rhythm if the heart rhythm is regular, the rate is 60-100bpm, and the PR intervals, the QT intervals, and the QRS complexes are within normal limits.

Echocardiography

Echocardiography is a safe, painless and non-invasive method of providing information about cardiac cavity dimensions (tamponade, pericardial effusion), the motion of valve leaflets and the presence of vegetation (subacute endocarditis, regurgitation) and the motion of ventricles during systole and diastole.

Indications

· bedside evaluation of disorders of the valves

· diagnosis of pericardial tamponade and pericardial effusion

· estimation of force of contraction of the left ventricle

· exclusion of intra ventricular thrombi and detection of chamber dilation and hypertrophy