Different rhythms

What is the most common adult rhythm with rates between 60-100/minute? The QRS is most often narrow with upright P waves in Lead II.

• Sinus bradycardia

• Second degree AV block

• First degree AV block

• Normal Sinus rhythm

Answer explanation

Known as regular sinus rhythm (RSR) or normal sinus rhythm (NSR)

It usually has a narrow QRS. The rate is often limited to below 150 / minute.

• Sinus Bradycardia

• Sinus Tachycardia

• Third degree AV Block

• Sinus rhythm

Answer explanation

Most often results from increased sympathetic stimulation (i.e. due to pain, fever, increased oxygen demand, and/or hypovolemia).

Results from the development of a reentry circuit within the atria generating a loop that discharges impulses at a flutter rate of 250-350 / minute. IT is readily identified by the sawtooth baseline.

• Atrial flutter

• First degree AV block

• Sinus bradycardia

• Ventricular Fib

Answer explanation

Most often the AV junction passes every second (rate = 150, called a 2:1 response) or every fourth impulse(rate = 75, called a 4:1 response) through to the ventricles

What has rates greater than 50/minute may be well tolerated by healthy adults?

• Sinus bradycardia

• Ventricular tachycardia

• Sinus tachycardia

• Ventricular Fib

Answer explanation

Athletes may routinely be in sinus bradycardia due to an optimal cardiac stroke volume that requires less HR to yield acceptable cardiac output. Sinus bradycardia may also be produced with Vagal stimulation or due to Sick Sinus Syndrome. Expect a narrow QRS with upright P waves in Lead II.

A chaotic rhythm originating in the ventricles, resulting in no cardiac output.

• Ventricular tachycardia

• Sinus bradycardia

• Sinus rhythm

• Ventricular Fibrillation

Answer explanation

Coarse VFib is noted when the amplitude (height) of the rhythm is equal to or more than 3 mm. Fine VFib is less than 3 mm in height and signifies less electrical energy within the myocardium - less opportunity for a successful defibrillation.

Is a heart rhythm disorder (arrhythmia) caused by abnormal electrical signals in the lower chambers of the heart (ventricles).

• Sinus rhythm

• Sinus bradycardia

• Ventricular tachycardia

• Sinus tachycardia

Answer explanation

results in hemodynamic compromise (due to minimal ventricular filling time and the absence of atrial kick). What makes this rhythm more ominous is its tendency to transition into ventricular fibrillation. Causes of VT include myocardial ischemia, a PVC landing on a T wave (R-on-T ), cardiac drug toxicity and electrolyte imbalance. Non-sustained VT (a group of 3 or more PVCs) is a run of VT.

Is almost always a disease of the AV node.

• Third degree AV Block

• First degree AV block

• Second degree AV block Type I (Wenckebach or Mobitz Type I)

• Sinus tachycardia

Answer explanation

results from a cyclical and progressive conduction delay through the AV junction. The ECG presents with a cyclical lengthening of the PR interval followed by a dropped QRS - a P wave not partnered with a QRS. The QRS complexes yield an irregular rhythm. Second degree AV block Type I may be caused by enhanced vagal tone, myocardial ischemia or the effects of drugs such as calcium-channel blockers, digitalis and beta-blockers.

There is complete absence of AV conduction – none of the supraventricular impulses are conducted to the ventricles.

• Third degree AV block (complete heart block)

• Ventricular tachycardia

• Ventricular tachycardia

• Normal sinus rhythm

Answer explanation

often an ominous rhythm requiring close monitoring for hemodynamic compromise, progression to ventricular standstill or asystole and other lethal dysrhythmias. Significant characteristics of this rhythm are: 1) lonely P waves - P wave without an accompanied QRS complex; and 2) chaotic PR intervals. A narrow QRS denotes a higher junctional block while a wide QRS points more towards a sub-nodal block high in the bundle branches.

Node block occurs when conduction through the AV node is slowed, thereby delaying the time it takes for the action potential to travel from the sinoatrial node through the AV node, and to the ventricles.

• Sinus Bradycardia

• Ventricular Fib

• First degree AV block

• Ventricular tachycardia

Answer explanation

results from a prolonged transmission of the electrical impulse through the AV junction (AV node and the Bundle of His). The significant finding of this rhythm is a prolonged PR interval of more than .20 seconds. The underlying rhythm should be identified and named prior to claiming a first degree AV block. For example, this rhythm is a normal sinus rhythm WITH a first degree AV block.

Indicates significant conduction disease in this His-Purkinje system and is irreversible. This irregular rhythm requires close monitoring: 1) low cardiac output is likely when multiple dropped QRS complexes occur; and 2) this rhythm can progress to complete heart block (third degree AVB).

• Sinus Tachycardia

• Complete heart block

• Second Degree AV Block Type II

• Ventricular Fib

Answer explanation

is typically caused by an intermittent block (interrupted supraventricular impulse) below the AV node. One or more QRS complexes are dropped with PR intervals that do not change (fixed PR interval).