From the Guidelines
For a patient presenting with a supraventricular regular rhythm on ECG with hidden P waves, the first line of management should be vagal maneuvers and/or IV adenosine (Class I) as recommended by the 2015 ACC/AHA/HRS guideline for the management of adult patients with supraventricular tachycardia 1. This approach is based on the principle of attempting to terminate the supraventricular tachycardia (SVT) using the least invasive methods first. The hidden P waves suggest that the rhythm may be driven by a focus within the atria or the atrioventricular (AV) junction, and adenosine can help differentiate between these possibilities by temporarily blocking AV nodal conduction.
Key Considerations
- The patient's hemodynamic stability is crucial in determining the urgency and approach to management.
- If the patient is unstable, immediate intervention such as cardioversion may be necessary.
- For stable patients, after attempting vagal maneuvers and/or adenosine, further diagnosis may involve analyzing the ECG for clues about the origin of the tachycardia, such as the presence of a long RP interval which is typical of atrial tachycardia (AT) because the rhythm is driven by the atrium and conducts normally to the ventricles 1.
- It's also important to consider and rule out other causes of tachycardia, including but not limited to hyperthyroidism, anemia, dehydration, pain, and the use of exogenous substances or drugs of abuse, as outlined in the guidelines for managing supraventricular tachycardia 1.
Management Approach
- Vagal maneuvers should be the initial step in managing a stable patient with supraventricular regular rhythm and hidden P waves, as they are non-invasive and can be effective in terminating the arrhythmia.
- IV adenosine is recommended if vagal maneuvers are ineffective or not feasible, given its efficacy in converting SVT to sinus rhythm and its diagnostic utility in differentiating between types of SVT.
- Further management, including the use of other medications or interventions like cardioversion, should be guided by the patient's response to initial therapy, their underlying cardiac structure and function, and the presence of any underlying conditions that may be contributing to the arrhythmia.
From the Research
Supraventricular Regular Rhythm on ECG with Hidden P Wave
- A supraventricular regular rhythm on an ECG with a hidden P wave is often associated with paroxysmal supraventricular tachycardia (PSVT) 2, 3.
- PSVT is characterized by a regular tachycardia rhythm with sudden onset and abrupt termination, and is caused by re-entry due to the presence of inhomogeneous, accessory, or concealed conducting pathways 2.
- The electrocardiogram (ECG) demonstrates a narrow QRS complex and regular tachycardia with hidden or inverted P waves 2, 3.
- The P wave is usually hidden within the QRS complex in cases of atrioventricular nodal reentry, which is the most common form of PSVT 3.
Diagnosis and Management
- Diagnosis of PSVT is based on the ECG findings, including a narrow QRS complex and regular tachycardia with hidden or inverted P waves 2, 3.
- Management of PSVT includes vagal maneuvers, such as the Valsalva maneuver, as a first-line treatment in stable patients 4, 5, 6.
- Adenosine is also used as a first-line agent to treat PSVT, and has been shown to be effective in terminating the arrhythmia 3.
- In cases where vagal maneuvers and adenosine are not effective, cardioversion or other pharmacological agents may be used to terminate the arrhythmia 2, 3.
Valsalva Maneuver
- The Valsalva maneuver is a non-invasive technique that involves increasing intrathoracic pressure to stimulate baroreceptor activity and increase parasympathetic tone 6.
- The effectiveness of the Valsalva maneuver in terminating SVT has been studied in several trials, with varying results 5, 6.
- A Cochrane review found that the evidence for the effectiveness of the Valsalva maneuver in terminating SVT was limited, and further research is needed to determine its efficacy 6.