Methods
Study design
This study involved a retrospective analysis of data from seven patients
who were admitted to our treatment center between December 2022 and
January 2023 for ICD shock or ventricular arrhythmias after SARS-CoV-2
infection. All patients signed an informed consent form, and the study
complied with the Declaration of Helsinki.
Data collection
The enrolled patients’ clinical data were collected and recorded,
including primary data such as age and sex, device type and model,
underlying disease, New York Heart Association (NYHA) cardiac function
classification, and presence of comorbid diseases. Data related to
device parameters and events, such as the ICD parameter settings,
treatment type and frequency, arrhythmia type, and termination mode were
also collected. Ancillary examination data were also obtained, including
data from electrocardiograms and cardiac ultrasounds, as well as
concentrations of electrolytes, markers of myocardial injury, and
N-terminal pro-B-type natriuretic peptide (NT-proBNP).
Definitions related to ICD treatment of the study
Appropriate ICD treatment was defined as the correct treatment selection
and delivery for persistent ventricular and hemodynamically unstable
arrhythmias.
Inappropriate ICD treatment was defined as an inappropriate response
to any signals other than those related to sustained ventricular and
hemodynamically unstable arrhythmias.
The default event termination criteria of the ICDs were defined as eight
consecutive intervals greater than or equal to the programmed diagnostic
tachycardia circumference after antitachycardia pacing (ATP) or shock
therapy.
The clinically recognized criteria for ICD treatment success were
defined as the successful conversion of arrhythmia to sinus rhythm and
its maintenance.
Ventricular electrical storm was defined as three or more sustained
ventricular arrhythmic episodes occurring at least 5 min apart within a
24-h period, with each episode requiring termination by the
intervention.13
Determination of the cause of inappropriate electroshock treatment
Following ICD treatment, two skilled deputy chief physicians with
experience in electrophysiology ascertained the appropriateness of the
electroshock treatment by examining the simulated body surface and
intracavitary electrograms obtained through the program controls in
conjunction with the patient’s clinical condition. If the two deputy
chief physicians’ assessments were in disagreement, consensus was based
on the chief physician’s assessment. This methodology was crucial for
identifying the causes of any inappropriate electroshock treatments.
Results
The baseline characteristics of the patients are shown in Table 1. The
mean age was 67±10 years (range: 51–78 years). Six patients were male
and one was female patient. Six of the seven patients had an ICD
implanted for the treatment of ischemic cardiomyopathy; the other had an
ICD implanted for the treatment of long QT syndrome. Two patients had
implanted CRT-Ds (Medtronic, DTBC2QQ), whereas the remaining five had
ICDs (Medtronic, BVAC). Four patients received ICDs for primary
prevention for the treatment of ischemic cardiomyopathy with a low left
ventricular ejection fraction (LVEF). One patient received ICDs for the
secondary prevention of long QT syndrome with frequent torsades de
pointes. Two patients received ICDs for the secondary prevention of
ischemic cardiomyopathy with VT. The mean time since device implantation
was 40±18 months.
The patient implant device settings are shown in Table 2. In one patient
with atrial fibrillation (AF) at the time of implantation, the VF
diagnostic interval was set to 270 ms to avoid inappropriate shock of
the CRT-D due to AF, with as rapid a ventricular rate as possible. In
another patient, the VT diagnostic interval was set to 390 ms based on
the ventricular rate measured during previous VT episodes to optimize
the device’s ability to recognize VT as much as possible and provide
treatment as early as possible to terminate the event.
The types of arrhythmias and the characteristics of the treatments
administered by the devices for each of the seven patients are shown in
Table 3. In seven patients, the average time between the initial onset
of symptoms of COVID-19 infection and device shock was 9±5 days (range:
3–20 days). The average QT interval was 460±46 ms (range: 386–536 ms)
in the seven patients; however, six patients exhibited QT intervals
exceeding 440 ms. Five patients exhibited a significant prolongation of
the QT interval after COVID-19 infection compared with the QT interval
measured at the time of device implantation.
Review of the program control data from the patients’ records revealed
that seven patients received a combined total of 54 ATP treatments, all
of which satisfied the default ICD criteria for event termination,
including one case that fulfilled the clinically determined criteria for
successful treatment. Additionally, four patients briefly exhibited
evidence of sinus rhythm recovery following ATP treatment, with the
event ultimately terminated by shock delivery. Another patient with a
low ventricular rate during a VT episode resulting from long-term
β-blocker use did not undergo ATP treatment or receive a shock; that
patient was placed on a programmed ICD for in vivodefibrillation, which briefly restored the rhythm before recurrence,
with the VT episode eventually being terminated via external
defibrillation (see Case 2 for details). In total, the seven patients
experienced 80 ICD shocks post-infection, 71 (88.75%) of which were
administered for VT and nine (11.25%) of which were administered for
AF; overall, this resulted in 66 successful terminations of arrhythmic
events (82.5% effective). In total, ATP therapy was administered 54
times, resulting in the successful termination of 48 of these arrhythmic
events. Five of the seven patients received appropriate treatment; two
patients received inappropriate treatment. Three of the seven patients
experienced ventricular electrical storms, with a single patient
receiving shocks and ATP treatment with the greatest frequency (at 53
and 35, respectively; see Case 1 for details). The remaining four
patients did not meet the diagnostic criteria for ventricular electrical
storms, although they did receive shocks or ATP treatment multiple times
within a single day.
The laboratory examination results are presented in Table 4. All
patients exhibited symptoms of SARS-CoV-2 infection and tested positive
for nucleic acids before admission. All patients demonstrated leukocyte
and creatinine levels either within the normal range or only slightly
elevated; with the exception of Case 2, who exhibited significantly
elevated levels of both leukocytes and creatinine. Seven patients
presented with varying degrees of electrolyte imbalance, which was
primarily characterized by low blood concentrations of potassium and
calcium. Six patients exhibited potassium levels below 4.0 mmol/L
(range: 3.5–3.9 mmol/L), and five of the seven patients had blood
calcium levels lower than 2.11 mmol/L. Troponin levels were elevated in
five of the seven patients (range: 0.023–0.297 ng/mL). Additionally,
all patients exhibited significantly elevated NT-proBNP concentrations
at the time of admission (range: 608.8–25,758 pg/mL). The
characteristics of two cases are described in more detail.
Case 1: A 78-year-old male with ischemic cardiomyopathy
underwent CRT-D implantation for primary prevention four years
previously. One week prior, he became infected with SARS-CoV-2 and was
referred to our institution due to experiencing recurrent shocks from
the device. Upon admission, the program control data revealed recurrent
VT, with 35 and 53 episodes of ATP treatment and shock, respectively.
His blood pressure and heart rate were unstable, with a maximum heart
rate of 202 beats/min. The program control data revealed that each ATP
treatment could terminate the tachycardia; however, sinus rhythm could
not be maintained continuously. While monitored by an external
defibrillator, his device underwent programming to augment the number of
ATP treatments and abbreviate the VF diagnostic interval to mitigate
shock administration. After ATP treatment, the patient received
intravenous antiarrhythmic medications, including amiodarone, lidocaine,
and esmolol. His blood pressure returned to normal after one day and
remained stable.
Case 2: A 55-year-old male with ischemic cardiomyopathy and
paroxysmal VT received an ICD for secondary prevention three years ago.
The patient became infected with SARS-CoV-2 11 days before presentation
and developed fever, palpitations, and muscle weakness. Two days before
presentation, these symptoms worsened and were accompanied by dyspnea
and an inability to lie down; therefore, he visited our institution.
Upon admission, his physical condition was characterized by a
temperature of 36.0 ℃, blood pressure of 81/67 mmHg, and oxygen
saturation of 85% in a non-oxygenated state, with wet rales in both
lungs. The program suggested that he was experiencing sustained VT, with
a heart rate fluctuating between 145 and 157 beats/min. No ATP or shock
therapy was administered because the ventricular rate had not entered
the VT/VF diagnostic interval of the program. He was administered
intravenous amiodarone and received active anti-heart failure (HF)
treatment. Arterial blood gas analysis indicated metabolic acidosis and
type I respiratory failure, and chest computed tomography indicated
diffuse, exudative lung changes, suggesting the possibility of viral
pneumonia. He received ventilator-assisted respiration, antiviral drugs,
antibiotic treatment with meropenem, and anti-inflammatory treatment
with methylprednisolone. However, his condition did not improve,
multiorgan failure developed, and he died eight days after admission.