What caused a patient in his 60s to develop intermittent palpitations and periodic weakness?
The patients who visited the emergency room had no significant health issues before the onset of the symptoms, and no family history of significant health problems, said Zhibin Lu, M.D., Ph.D., of Zhongnan Hospital of Wuhan University in China, and colleagues. JAMA Internal Medicine.
Physical examination revealed arrhythmia and blood pressure of 92/58 mm Hg. The medical team initially performed a 12-lead electrocardiogram, which revealed a short sinus rhythm followed by a wide complex tachycardia.
Lu and team described the most significant ECG finding as a wide QRS complex tachycardia that “initially exhibited a right bundle branch block (RBBB)-like pattern in the first two wide QRS complexes, then stabilized to a left bundle branch block (LBBB)-like pattern in the fourth through seventh complexes.”
They identified the third beat as a fusion beat and also noted evidence of atrioventricular dissociation, coupled with an early dominant R wave in lead aVR and a QS/rS pattern in lead V.3 To V6These findings suggest a diagnosis of ventricular tachycardia, the researchers said.
When the team examined the inferior and precordial leads during episodes of ventricular tachycardia, they found a small deflection after the QRS complex that was only evident in RBBB-like beats. Short sinus rhythm showed RBBB, low voltage, QRS complexes, and T-wave inversions in leads II and V.2 To VFour.
Furthermore, the QRS complexes revealed terminal deflections that were more prominent in the corresponding leads during sinus rhythm, and these were considered to be epsilon waves.
The patient underwent echocardiography, which revealed right ventricular (RV) hypokinesis, right atrial and ventricular dilation, and severe tricuspid regurgitation. Cardiac MRI “confirmed global RV hypokinesis and the anterior and inferior RV myocardium, particularly with fibrofatty infiltration within the interventricular septum, on postcontrast hyperenhanced images,” Lu et al. write.
Nevertheless, neither the electrocardiogram nor cardiac MRI findings showed any abnormal left ventricular (LV) function. The patient underwent genetic testing, but no relevant genetic mutations were detected. The patient was advised to undergo electrophysiological testing, but this was refused.
Lu and colleagues noted that the available results met two major and two minor Padua criteria, and therefore they made a provisional diagnosis of arrhythmogenic right ventricular cardiomyopathy (ARVC).
The team deemed the patient at moderate risk for ventricular arrhythmias based on evidence of moderate right ventricular dysfunction, episodes of intermittent ventricular tachycardia, and no history of syncope or sudden cardiac death. The patient then received an implantable cardioverter-defibrillator along with medical therapy.
Discussion
ARVC is a genetic disorder that affects the right or both ventricles. It is characterized by fibrofatty tissue infiltration or replacement of the myocardium. ARVC can lead to potentially fatal ventricular arrhythmias, the authors note. Patients, especially young athletes, may present with syncopal episodes and sudden cardiac death.
Lu and his team said a definitive diagnosis would require a comprehensive evaluation that includes myocardial structure, function, family history, and genetic testing, but an electrocardiogram could be helpful in assessing the presence of ventricular arrhythmias and depolarization and repolarization abnormalities.
Of note, one review of risk stratification suggests that pathogenic variants may be identified in more than 60% of patients with ARVC. “Consistent with this, genetic testing has emerged as an important diagnostic tool and is critical for cascade family screening,” the review authors wrote.
Traditionally, the presence of epsilon waves on an ECG has been considered a hallmark of ARVC, Lu and his coauthors note, but recent reports have shown that epsilon waves can be seen in several conditions involving RV enlargement, damage, or necrosis, including coronary artery disease, cardiac sarcoidosis, congenital heart disease, and RV myocardial infarction.
Moreover, “epsilon waves are not limited to supraventricular rhythms but are also observed in ventricular tachycardias such as RBBB,” Lu et al. wrote. In this patient’s case, the disappearance of epsilon waves in LBBB-like beats suggests an alternative cause of ventricular tachycardia.
Typically, RBBB-like ventricular activation patterns originate in the left ventricle, leading to ventricular dyssynchrony and revealing epsilon waves in the right ventricle, the researchers explained. In contrast, ventricular activation originating from the right ventricle delays left ventricular depolarization, making the epsilon wave less visible.
“The deflection following the broad complex must be distinguished from retrograde P waves in ventricular rhythm and the intrinsic conduction delay of RBBB,” the authors note. “In this case, the PP interval can be measured by the first two sinus beats, allowing the location of subsequent potential sinus P waves during ventricular tachycardia to be inferred.”
This led clinicians to identify deflections observed in RBBB-like rhythms as epsilon waves rather than retrograde P waves.
“Furthermore, the terminal delay vector of the RBBB points in a right frontal direction, allowing the observation of S waves in leads I, aVL, and V.Fiveand V6 “In the right precordial leads, epsilon waves as well as R waves are seen,” Lu et al. write. “In contrast, the polarity and direction of epsilon waves cannot be determined due to their undulating, small-spike pattern, and their distribution on the ECG depends on the specific ventricular region involved. However, it is not uncommon for epsilon waves and RBBB to coexist in one patient.”
Although it is possible to detect epsilon waves in ventricular tachycardia, it is important to consider retrograde P waves when broad waveforms are followed by repeated deflections, the researchers added. “Careful recognition of hidden sinus P waves in ventricular tachycardia may lead to a differential diagnosis.”
“Prompt placement of an implantable cardioverter-defibrillator is not necessary for all patients. “Appropriate risk assessment and medical strategies can lead to significantly improved patient outcomes,” Lu and colleagues conclude.
Disclosures
The authors report no conflicts of interest.
Primary information
JAMA Internal Medicine
Citation reference: Li Y, et al. “Missed small waves in wide rate complex tachycardia” JAMA Intern Med 2024; DOI: 10.1001/jamainternmed.2023.7883.