A practical protocol to address barriers and slow acceptance for use of
continuous ischemia monitoring in US hospitals
Kristin E. Sandau, PhD, RN,
a
Maureen Smith, RN, MSN, CCNS,
b
(
a
Bethel
University and United Hospital, St. Paul, MN, USA;
b
Nasseff Heart Center,
United Hospital, St. Paul, MN, USA)
Background: In 2004, a Scientific Statement of practice standards for in-
hospital cardiac monitoring was published by the American Heart Association
and endorsed by the International Society of Computerized Electrocardiology
(ISCE), including recommendations for continuous ischemia (cST-seg)
monitoring. In 2007, the author sent an electronic survey nationally to a
random sample of 915 cardiologists from a pool of 4985 certified cardiologists
registered with the electronic vendor, Epocrates. Of hospitals where
respondents admitted patients, 49% had a standard of practice for using cST-
seg monitoring for cardiac patients. Most responding cardiologists selected
early identification of potential ischemia (83.5%) and early identification of
reocclusion after percutaneous coronary intervention (PCI) (74%) as benefits of
cST-seg monitoring. Regarding barriers, false-positive alarms for ischemia had
the highest level of agreement as a barrier to cST-seg monitoring (61.5%),
followed by lack of understanding for use of this technology by nursing staff
(56.5%), extra telephone calls to you or your partners that you felt were based
on inaccurate monitoring (48%), lack of understanding of this technology by
other physicians (47%), and extra cost or treatment due to false-positive alarms
(43%). More positive perceptions of benefit and clinical usefulness of cST-seg
monitoring were reported by cardiologists who practice in hospitals that were
implementing cST-seg monitoring guidelines.
Conclusion: For practice standards to be incorporated into routine practice
nationally, successful interdisciplinary protocols need to be shared. Thus, we
are sharing our 572-bed hospital's protocol for cST-seg monitoring in effort
to address specific barriers. An interdisciplinary team created the cST
monitoring protocol, which stipulates that the ST alarm default is in the “on”
setting for all patients. Thus, nurses must manually turn ST alarms to “off” for
patients who meet exclusion criteria (intraventricular conduction defect,
paced rhythm, known pericarditis or myocardial contusion, ST-segment
“sagging” due to digoxin). Before notifying the physician about an ST alarm,
the nurse first verifies that the patient's patches are correctly placed and that
the alarms are not due to artifact, particularly from patient movement. Next,
for any 2-mm ST change sustained for 15 minutes (with or without
symptoms), the nurse obtains a prn 12-lead ECG to confirm ST changes are
present. The resident is paged to confirm suspected ischemia on the 12-lead
before the attending physician is called. By following this protocol, we are
able to reduce unnecessary telephone calls for false alarms and have
interdisciplinary, hospital-wide cooperation for cST-seg monitoring.
doi:10.1016/j.jelectrocard.2009.08.040
Cardiac restitution and electrocardiographic stress testing
C.P. Danford, V. Varadarajan, A.J. Starobin, V.N. Polotski, J.M. Starobin,
( Mediwave Star Technology, Inc., Greensboro, NC, USA; and University
of North Carolina at Greensboro, Greensboro, NC, USA)
Background: Understanding the relationship between cardiac restitution
and the development of arrhythmias remains a key task for the study of
cardiac electrical dynamics. Although the physical phenomena involved in
initiation of electrical instabilities are dauntingly complex, there exist
reduced models of cardiac tissue that reproduce characteristic features of
cardiac restitution and possess the advantage of being analytically solvable.
In such models, concepts such as a threshold for cardiac alternans can be
framed in terms of a few parameters of the excitable system. Their study
could provide a theoretical foundation for validation of potential clinically
viable methods of diagnosis of cardiac abnormality based on electrocardio-
gram stress testing.
Method: Electrical pulse propagation in an excitable cable was analyzed
using the 2-variable Chernyak-Starobin-Cohen reaction-diffusion system
with pacing rate-dependent excitation threshold. This allowed us to control
the amount of model memory while still using the simplicity of an
analytical approach. The cable was paced at one end with square pulses to
simulate traditional steady-state and S1-S2 pacing sequences. As in
experimental protocols, the pacing interval was decremented in a stepwise
manner until conduction block occurred at higher pacing rates. Excitation
pulse duration, refractory period, and wavefront speed were computed
numerically and were compared with the analytical solution of the
Chernyak-Starobin-Cohen model.
Results: We observed that restitution and hysteresis depend on the relationship
between pacing period and steady-state excitation threshold and also on the rate
of excitation threshold adaptation after an abrupt change in pacing period. We
also observed that the onset of action potential duration alternans is determined
by a minimal pulse duration and maximal excitation threshold, which could be
approximated by the analytical critical pulse duration and excitation threshold
of a stable solitary pulse. This approximation was independent of the
magnitude of the slopes of restitution curves, the adaptation constant of
excitation threshold, or its dependence on pacing interval.
Conclusion: These theoretical findings have strong implications for stress-
test electrocardiogram analysis of cardiac restitution and alternans.
doi:10.1016/j.jelectrocard.2009.08.041
Ventricular preexcitation mimicking dilated cardiomyopathy: the
location of the accessory pathway is predictive of this association
Floris Udink ten Cate, ( University of Köln, Köln, Germany)
Background: Ventricular preexcitation is common in childhood. Dilated
cardiomyopathy may arise in such patients as a result of recurrent or long-
standing tachyarrhythmia. We demonstrated a causal relationship between
ventricular preexcitation and dilated cardiomyopathy, in the absence of
proven recurrent tachyarrhythmias. This relationship seems to depend on the
location of the accessory pathway.
Patients and Methods: Ten consecutive children, ranging in age between
0.6 and 17 years, were studied. All of them had over ventricular
preexcitation on the 12-lead ECG. The vector of the accessory pathway
suggested a right-sided, septally located pathway in all patients. None of the
patients had had a documented tachyarrhythmia; however, all of them had
evidence for dilated cardiomyopathy, with left ventricular end diasolic
pressure (LVEDD) more than 97th centile for weight and a left ventricular
fractional shortening (LVFS) of less than 25% on M-mode echocardiogra-
phy. Based on these findings, diagnostic cardiac catheterization was
performed in 4 of 10 patients; in all of whom, the LVEDP was normal.
Myocardial biopsies were also obtained in these patients, and the findings
were not diagnostic for myocarditis. Metabolic screening, family history,
and viral screening were all negative.
Procedures and Results: Eight of the 10 patients underwent invasive
electrophysiological (EP) study, despite the absence of symptoms suggestive
of tachyarrhythmia, and in the absence of a documented reentrant
taychcardia. The accessory pathway had a right-sided septal location in 7
patients, whereas 1 young girl had a right-sided fasciculoventricular
pathway (hitherto considered to be a benign finding). The pathways were
successfully ablated in all 8 patients (radio frequency [RF] ablation in 7,
cryoablation in 1). Of the remaining 2 patients, both had spontaneous loss of
ventricular preexcitation during follow-up. Surprisingly, loss of preexcita-
tion (either after ablation or spontaneously) was associated with complete
recovery of left ventricular function in 9 of 10 patients, with improved
function in the last patient in the series.
Conclusions: Right-sided septal pathways with overt ventricular preexcita-
tion may result in marked ventricular dyssynchrony, which mimics dilated
cardiomyopathy. A causal association between such pathways and apparent
dilated cardiomyopathy is suggested by the rapid normalization of
ventricular function after loss of preexcitation. It is as yet unclear why
only some children seem to develop this form of cardiomyopathy.
doi:10.1016/j.jelectrocard.2009.08.042
Human overread of semiautomated QT measurements may adversely
affect
final results in cardiac safety studies
Branislav Vajdić, Ihor Gussak, Boško Bojović, Samuel George, ( New-
Cardio, Inc, Santa Clara, CA, USA)
619Poster Session 2 / Journal of Electrocardiology 42 (2009) 614–621