- Junctional premature beat can simulate a first degree AV block by concealed retrograde conduction into AV node.
– Consider a “hidden” JPB if there is sudden unexplained prolongation of PR interval.
- Hypokalemia can cause weakness by hypokalemic periodic paralysis. Do an ECG for patient with unexplained weakness !
- Pericardial tamponade: look for low QRS voltage (sum of R wave in limb leads < 5mm, in precordial leads <10mm) + tachycardia, electrical alternans can help but not always present
- Bix rule: if a P-wave is located halfway between two QRS complexes, there’s a good chance there is also a P-wave buried inside the QRS as well. It is normally an atrial flutter with 2:1 conduction
P waves in the middle of two QRS complexes