Diagnoses of arrhythmia
Noninvasive diagnosis of arrhythmias
Arrhythmias can be documented by a regular ECG performed at the time that the patient is having symptoms if they go to the emergency room or to their physician. Patients who have daily episodes of arrhythmia can have a 24-hour holter monitor placed to document which arrhythmia is present. More commonly, patients may have less frequent e.g. monthly episodes and can use an external event monitor to record their heart rhythm and transmit it telephonically.
Very rare (e.g. yearly) episodes are difficult to document unless the patient waits until an episode occurs and then seeks medical attention at an emergency room or physician’s office. Patients who call 911 may have their episode of arrhythmia documented by the paramedics who can perform an ECG en route to the hospital. Hospitalized patients on a telemetry monitor when the arrhythmia occurs may have it documented in that way. Internal looped monitors may be implanted to document arrhythmias when other means fail. These devices are capable of automatically recording an ECG if an arrhythmia occurs. The device has continuously in its memory buffer the previous 5 minutes of the patient’s rhythm and if activated by the patient or a family member (in the case of syncope) usually records the arrhythmia. The patient can then visit their doctor’s office, and the nurse can place a communicating wand on the skin over the device and retrieve the rhythm information.
Invasive diagnosis of arrhythmias
The definitive diagnosis of an arrhythmia usually requires an EP study be performed to assess the normal heart electrical system and find out what arrhythmias are possible. After some degree of general anesthesia (usually just IV propofol), local anesthesia is used to insert venous sheaths in the femoral and/or subclavian/internal jugular veins. Through these sheaths, long plastic catheters with ring electrodes can be placed using fluoroscopy to precise positions in the heart. They can record electrograms from these sites; they are displayed on a monitor for the electrophysiologist to study. Also, a special computer pacemaker controlled by the electrophysiologist can pace the heart speeding it up and putting in extra beats to try to induce the arrhythmia. This is referred to as programmed electrical stimulation. In this way the entire normal heart electrical system can be assessed. Sometimes, the arrhythmia cannot be induced. In these cases, repeating the pacing after giving isoproterenol may reveal the arrhythmia. Rarely, this also fails to induce the arrhythmias, and the patient must be allowed to fully awaken. After all of these maneuvers, the patient’s arrhythmia can be induced in over 95% of the cases.