Sympathetic toggled sinus rate acceleration as a mechanism of sustained sinus tachycardia in chronic orthostatic intolerance syndrome

Sympathetic toggled paroxysmal atrial fibrillation and recurrent premature atrial contractions in ambulatory patients

BACKGROUND

Autonomic nerve activity is important in the mechanisms of paroxysmal atrial fibrillation (PAF).

OBJECTIVE

To test the hypothesis that a single burst of skin sympathetic nerve activity (SKNA) can toggle on and off PAF or premature atrial contraction (PAC) clusters.

METHODS

We performed neuECG recording over 7 days in patients with PAF.

RESULTS

In Study 1, we found 8 patients (7 men, 1 woman, 62±8 years) had 124 episodes of PAF. An SKNA burst toggled both on and off PAF in 8 (6.5%) episodes (Type 1), toggled on but not off in 12 (9.7%) episodes (Type 2), and toggled on a PAC cluster, followed by PAF in 4 (3.2%) episodes (Type 3). The duration of these PAF episodes was < 10 min. The remaining 100 (80.6%) episodes were associated with active SKNA bursts throughout PAF (Type 4) and lasted longer than Type 1 (p=0.0185) and Type 2 (p=0.0027) PAF. There were 47 PAC clusters. Among them, 24 (51.1%) were toggled on and off, and 23 (48.9%) were toggled on but not off by an SKNA burst. In Study 2, we found 17 patients (9 men, 8 women, 58±12 years) with < 10 min PAF (4, 8, 0, and 31 of Types 1-4, respectively). There were significant circadian variations of all types of PAF.

CONCLUSIONS

A single SKNA burst can toggle short-duration PAF and PAC cluster episodes on and off. The absence of continued SKNA after the onset might have affected the maintenance of these arrhythmias.

Postural orthostatic tachycardia syndrome after COVID-19 vaccination

BACKGROUND

There is an association between coronavirus disease 2019 (COVID-19) mRNA vaccination and the incidence or exacerbation of postural orthostatic tachycardia syndrome (POTS).

OBJECTIVE

The purpose of this study was to characterize patients reporting new or exacerbated POTS after receiving the mRNA COVID-19 vaccine.

METHODS

We prospectively collected data from sequential patients in a POTS clinic between July 2021 and June 2022 reporting new or exacerbated POTS symptoms after COVID-19 vaccination. Heart rate variability (HRV) and skin sympathetic nerve activity (SKNA) were compared against those of 24 healthy controls.

RESULTS

Ten patients (6 women and 4 men; age 41.5 ± 7.9 years) met inclusion criteria. Four patients had standing norepinephrine levels > 600 pg/mL. All patients had conditions that could raise POTS risk, including previous COVID-19 infection (N = 4), hypermobile Ehlers-Danlos syndrome (N = 6), mast cell activation syndrome (N = 6), and autoimmune (N = 7), cardiac (N = 7), neurological (N = 6), or gastrointestinal conditions (N = 4). HRV analysis indicated a lower ambulatory root mean square of successive differences (46.19 ±24 ms; P = .042) vs control (72.49 ± 40.8 ms). SKNA showed a reduced mean amplitude (0.97 ± 0.052 μV; P = .011) vs control (1.2 ± 0.31 μV) and burst amplitude (1.67 ± 0.16 μV; P = .018) vs control (4. 3 ± 4.3 μV). After 417.2 ± 131.4 days of follow-up, all patients reported improvement with the usual POTS care, although 2 with COVID-19 reinfection and 1 with small fiber neuropathy did have relapses of POTS symptoms.

CONCLUSION

All patients with postvaccination POTS had pre-existing conditions. There was no evidence of myocardial injuries or echocardiographic abnormalities. The decreased HRV suggests a sympathetic dominant state. Although all patients improved with guideline-directed care, there is a risk of relapse.