Introduction
An electrocardiogram or an ECG tracks the electrical activity of the heart. Soft electric pads are placed on the hands and feet of the patient to record the electric signals. An electrocardiogram has different gaps in between, called electrical intervals, which are denoted by alphabets corresponding to other heart functions. One such interval or gap is called the QRS interval. It is the most central part of an electrocardiogram report. The QRS interval lasts from 0.06 seconds to 0.10 seconds. It represents ventricular depolarization, which means the rapid increase in the pressure of the heart's ventricles.
The heart is sectioned into four chambers: two upper chambers called the atrium and two lower chambers called the ventricle. Ventricular depolarization is the event when the ventricles contract, thus increasing the pressure within the ventricles. When there is a change in this ventricular depolarization, it changes the QRS cycle interval and thus leads to a phenomenon known as the Ashman phenomenon. This phenomenon was first introduced by Ashman and Gouaux in 1947. It is necessary to understand this phenomenon because it helps diagnose complex conditions that show arrhythmia or irregular heartbeats.
What Causes the Ashman Phenomenon?
The unusual change in the ventricular depolarization leads to a typical heartbeat with arrhythmia of a long cycle followed by a short cycle. This is commonly referred to as the Ashman beat. This beat is also seen in tachycardia, which means rapid heartbeat. RR refers to the true heartbeat within one’s body. An elongated RR interval followed by a short RR interval leads to a deviated and unusual QRS complex, and this entire phenomenon is called the Ashman phenomenon. The cause of the Ashman phenomenon is dependent on the changes in the refractory period of the heart muscles relative to the corresponding heart rate.
The refractory period refers to the moment when a nerve or muscle is not responsive due to an immediate stimulation. It is also referred to as action potential. A combination of long and short cycles of RR interval is likely due to alterations in a heartbeat; hence, the following QRS cycle had deviations. Thus, the Ashman phenomenon is caused mainly due to arrhythmias such as atrial fibrillation. Atrial fibrillation, which is a variant of arrhythmia, is one of the reasons associated with the Ashman phenomenon, as it corresponds to the change in the QRS complex.
What Is the Pathophysiology of the Ashman Phenomenon?
Ashman's phenomenon occurs in atrial fibrillation when not all atrial impulses are consistently conducted through the AV node, leading to variable RR cycle lengths and predisposing aberrant conduction. In atrial fibrillation, the refractory period of an impulse in the ventricular muscle varies with the RR cycle length. Longer RR cycles result in longer refractory periods, while shorter RR cycles lead to shorter refractory periods. This can cause a pattern resembling bundle branch block, predominantly right bundle branch block.
What Are the Signs and Symptoms of the Ashman Phenomenon?
A twelve-lead electrocardiography will present the clinical signs of the Ashman phenomenon. The baseline rhythm is read for any alterations in the QRS interval. There is no clinical manifestation of the Ashman phenomenon, and this is why the patients suffering from this disease do not show any signs or symptoms. Very rarely, patients may experience strong palpitations, lightheadedness, and difficulty breathing due to shortness of breath. Chest pain, dizziness, and syncope are also not very prevalent symptoms but have been reported. An irregularly irregular heart rhythm is also associated with the Ashman phenomenon. Patients may also experience ectopic heartbeat, which means the feeling of an extra heartbeat alongside tachycardia or rapid heartbeat. The physical examination represents an altered pulse rate. Electrolytes and metabolic abnormalities can lead to atrial fibrillations and, thus, the Ashman phenomenon. The action of drugs also holds the potential to change the standard heart rate and, eventually, the QRS interval.
How Can the Ashman Phenomenon Be Treated?
A physician should be aware of the emergency management of arrhythmia since it is one of the main reasons for the presence of the Ashman phenomenon. In case there are no symptoms, which is in the majority of the cases, no immediate treatment is necessary. In case there is an underlying cardiac condition, it needs to be managed first.
The reason is that the Ashman phenomenon is usually a complication or an effect of previously present cardiovascular disease. Bringing the abnormal heart rate to normal by treating arrhythmia, tachycardia, or whatever clinical manifestation is recorded is necessary. Different kinds of arrhythmia are initially treated, and then the underlying cardiovascular disease, if present, is managed therapeutically.
How to Diagnose the Ashman Phenomenon?
Electrocardiography, or ECG, is the go-to technology for diagnosing the Ashman phenomenon. No specific laboratory evaluations are needed for this phenomenon. Medical history should be recorded to consider any active underlying cardiovascular disease. Additionally, a thorough drug history is also recorded due to the heart's sensitivity toward reactions to certain drugs.
The Fisch criteria is one of the methods used in the diagnosis of the Ashman phenomenon. It checks the reading of an electrocardiogram wherein if there is a long cycle before a QRS interval or a short cycle before the QRS interval, leading to an aberrancy in the QRS interval, then it confirms the presence of the Ashman phenomenon. Other criteria under the Fisch criteria are multiple abnormalities of the QRS interval in a single electrocardiogram. The Ashman phenomenon may be suspected in cases of atrial fibrillation because atrial fibrillation is parallel to the RR and QRS findings of the Ashman phenomenon. Atrial fibrillation is the abnormal heart rate due to poor flow of blood to the heart.
Conclusion
The Ashman phenomenon is a physiological alteration in the QRS complex. It occurs due to arrhythmia or as a side effect of underlying cardiovascular diseases. It does not show any clear-cut symptom or sign, but a critical diagnostic benchstone is the Fisch criteria. Diagnosis is made when the electrocardiogram reading shows an abnormally long RR interval or an unusually short RR interval followed by an aberrant QRS complex where the RR interval represents the true heartbeat of an individual. Interpretation of the same is made through electrocardiograms, and treatment is dependent on the signs and symptoms. The impact of the Ashman phenomenon on quality of life is not entirely profound and can be managed easily with the awareness of diagnostic certainty.
