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an electrocardiogram is done is a likely predictor for most car-

diac outcomes. Similarly, the finding of unanticipated sagittal

sinus thrombosis on a CT scan or MRI will likely predict serious

neurological sequelae, again because CT scans of the head are

ordered in a subset of patients at risk for neurological events. In

their study, however, the authors analyzed data from the Cardio-

vascular Health Study (5577 participants) for a median of 12 years

of the primary cohort, and the Atherosclerosis Risk in Communities

Study (15,792 participants) for a median of 22 years as their rep-

lication cohort. Thus, by design, ascertainment bias is essentially

excluded and gives us reason to seriously examine the impact of

their findings in terms of pathophysiology and population-wide

screening.

PACs and AF

Paroxysmal AF often has discreet triggers that may manifest as

single PACs, bigeminy, couplets, or paroxysmal monomorphic atrial

tachycardia in addition to recorded AF. From their study, we can-

not glean whether the associated AF in patients with recorded

single PACs is paroxysmal or persistent. Furthermore, the loca-

tion of origin of the PACs, coupling interval, and whether or not

the absence of PACs on multiple electrocardiograms predicts

freedom from AF are unknown. Given the very high likelihood of

recordable AF in closely monitored patients with increasing age,

a possibility that the patients in the cohort with PACs were other-

wise at no higher risk for AF such as age, metabolic syndrome,

sleep apnea, etc is unclear.

PVCs and Congestive Heart Failure

Frequent PVCs as a possible sole cause for cardiomyopathy is

now well-established. At the same time, ventricular dysfunction

from many causes may present as or have associated PVCs. This

chicken and egg conundrum between PVCs and cardiomyopa-

thy is often difficult to solve, especially when multifocal PVCs are

present and detected after a cardiomyopathy was established. The

present study suggests that the electrical manifestation of PVCs

may well precede mechanical dysfunction (heart failure) either as

an early marker or as a cause.

Single-Lead Continuous Monitoring

There has been a plethora of devices for home and continuous

nonobtrusive cardiac monitoring. These vary from single-lead

electrocardiograms, pulse recordings, heart rate variability from

either of the two above, and similar devices that are integrated into

clothing, wearable devices, etc. Premature beats do not require

a 12-lead electrocardiogram to record and could easily be done

from single-lead recordings, and, indeed, with fairly simple trans-

forms and algorithms looking at pulse rate variability to diagnose,

quantify, and monitor. In the context of this burgeoning group of

devices and related technologies, the present study is timely and

important to integrate in future algorithm development.

The Issue of Death

A very important and nonintuitive finding from this study is that

a single premature beat, atrial or ventricular, is a marker of and

associated with the subsequent increased likelihood of death.

We cannot glean from this study and report whether the likeli-

hood of death is directly related to AF or heart failure but likely

presume this pathophysiological link. The link between AF and

death has been elusive to establish when reduction of preventa-

ble stroke and associated comorbidity is considered, and, further,

the possible incremental risk of PVCs over ventricular dysfunc-

tion alone with regard to cardiovascular mortality has also been

challenging. The present study with further analysis and repro-

duction from other cohorts may give us the answers that, in turn,

will leave difficult to answer questions on how aggressively we

need to monitor and intervene to prevent death when single pre-

mature beats are found.

Conclusion

A contemporary international leader – a teetotaler –

was asked why he doesn’t drink alcohol. The question

was posed as to why a single drink, particularly in a

social context, could possibly be harmful. The leader

who had bad family experiences with addiction and

alcoholism replied, “You can’t have two drags without

first having one!” Although a single premature beat

may seem innocuous, the mechanisms that underlie

the possibility of creating a single beat, particularly

with a re-entrant mechanism, establishes the

potential for repetitive manifestations of this building

block producing both arrhythmia and mechanical

dysfunction.

Dr Asirvatham is Consultant, Division of

Cardiovascular Diseases and Internal

Medicine, Division of Pediatric

Cardiology, Professor of Medicine and

Pediatrics Mayo Clinic College of

Medicine, Program Director EP

Fellowship Program, Director of

Strategic Collaborations Center for Innovation, Mayo

Clinic, Rochester, Minnesota.

Dr Kella is from the Department of Cardiovascular

Diseases, Mayo Clinic, Rochester, Minnesota.

ARRHYTHMIAS/HEART RHYTHM DISORDERS

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VOL. 2 • NO. 2 • 2017