In this systematic review and meta-analysis, we provide a high level of evidence results that are consistent with most studies done on the same issue. Our result showed that using the MVM in patients with SVT decreased the need for any emergency treatment by terminating the SVT with simple, cost-free, and well-tolerated intervention.
The efficacy of the valsalva maneuver is dependent on generating high intrathoracic pressure and stimulating baroreceptors in the carotid body and aortic arch leading to an increase in the vagal tone and venous return [9]. The subjectivity of straining efforts might explain the variation (in the efficacy) of SVM efficacy [10, 11]. This is a limitation in delivering this mode of therapy as it is heavily dependent on the instructions provided to the patients by the healthcare workers (i.e., emergency response personnel and physicians). This can explain the inconsistency in performing the valsalva maneuvers as it has been reported that only 9.6% of ED physicians would give specific instructions to their patient on the position and the duration, according to Taylor et al. [12]. Patients with recurrent SVT can be taught on how to perform MVM by blowing into a 10-ml syringe, which can result in the same intrathoracic pressure (equivalent to 40 mmHg of generated pressure) as an aneroid manometer yet widely available [9]. Addressing this limitation will lead to faster termination of SVT, reducing ED visits when the vagal maneuver is self-administered, shorter time in ED, lower need of administering IV medication, hospital admission, and cardioversion.
The passive leg rise suggested by Appelbaum et al. study will maximize the venous return which will increase the preload resulting in an increase in the cardiac output causing higher vagal tone response. Appelbaum et al. were the first systematically reported in a systematic method the merit of MVM. In RCT involving 428 patients, MVM was more effective in aborting SVT episodes when compared to SVM (43% vs. 17%) [2]. Following Appelbaum et al., Çorbacıoğlu et al., Ceylan et al., and Chen et al. all reported a better efficacy of MVM when compared to SVM (43% vs. 11%; 38% vs.12%; and 46% vs.16%, respectively) [2,3,4,5]. The description of MVM in each study was the same with minor changes. One modification in Chen et al. was the angle of 90° in raising the legs, which might produce a slightly higher success rate compared to the 45° described by other studies. This can be explained by the result presented in Chen et al. study and by the physiology of the maneuver and its effect on the baroreceptors [13]. Similar success rates were also reported in a published abstract by Youssef et al. (MVM 47% vs. SVM 20%) that we did not include in our meta-analysis due to lack of access to the full manuscript [14]. A case report is done by Appelboum et al. on a patient with a recurrent SVT over 30 occasions in 13 years. MVM was effective as a cardioversion in this patient when both adenosine and verapamil failed to terminate the recurring SVT [15]. A previous systematic review done by Wheeler suggested that the MVM increased the rate of termination of SVT termination in adult patients in the ER and proposed that making a standardization in valsalva maneuver can increase the effectiveness of vagal maneuvers [16]. Also, a study done by Mohammad et al. reported the overall rate success of MVM as 47.3% (44/93 patients); however, this study did not compare MVM and SVM, and for this reason, was not included our meta-analysis [17]. In our analysis, we found that adopting MVM leads to 2.5-fold increase in the rate of sinus rhythm and a 32% reduction in the risk of requiring of abortive antiarrhythmic medication in ED.
Carotid sinus massage is another modality commonly reported with limitations; its efficacy is not better than SVM [3], but the risk of stroke risk was a major limitation, especially in older patients [18, 19]. Appelbaum et al. reported minor adverse events with VM, including transient hypotension, nausea, and musculoskeletal pain, and did not find passive leg rise leads to be associated with more adverse events [2].
It is plausible to think that with the rapid elimination of SVT early in the encounter, we might reduce time in the ED, need for admission, and overall cost of care. Time spent in the ED was not different between the tested VMs in our analysis; both maneuvers take little or no time to perform. Also, the lack of standardized criteria for admission of SVT patients will limit the merit of a meta-analysis in answering such a question. A dedicated RCT with pre-determined admission criteria and a cost analysis plan will support the wide adoption of MVM as a first-line modality in patients presenting with SVT.
