Cardiovascular disease is the major cause of death globally, accounting for 17.9 million
deaths per year in 2019. Aside from the acute coronary syndrome, where percutaneous coronary
intervention (PCI) has been shown to improve outcome, the number of patients with chronic
coronary syndrome (CCS) is also increasing. PCI of hemodynamically relevant stenotic lesions
causing myocardial ischemia is the standard treatment in these patients. Effective
revascularization, as recommended by the European Society of Cardiology (ESC) guidelines,
requires to differentiate between hemodynamically relevant and non-significant stenotic
coronary lesions.
Currently, coronary stenosis assessment is performed by structural visual angiographic
assessment or by coronary pressure measurements up- and downstream of the lesion. The latter
is recommended by the ESC and is based on its prognostic value derived from large randomized
clinical trials. Given temporary paralysis of the coronary microcirculation by a
hyperemia-inducing substance such as adenosine (ADO), pressure is, in theory, directly
related to coronary flow. Therefore, the pressure drop during hyperemia across a coronary
stenosis, i.e., fractional flow reserve (FFR) provides an estimate of its restrictive effect
on flow. However, this method depends on expensive pressure sensor angioplasty guidewires,
and on hyperemia-inducing substances, such as ADO. Hence, pharmacologic limitations such as
atrioventricular conduction defects and asthma and other potential adverse events (e.g.
arrhythmias) aside from costs are major drawbacks of pressure-derived FFR. In order to avoid
potential drug-induced side effects and achieve maximal hyperemia, the study group performs
reactive hyperemia FFR measurements induced by a proximal, 1-minute coronary artery balloon
occlusion. This method has been documented non-inferior in its ability to detect relevant
coronary stenosis compared to adenosine-induced FFR.
The present project aims at validating a novel, potentially more harmless, faster and less
costly diagnostic approach for measuring hemodynamic coronary stenosis severity.
The commonly obtained surface lead electrocardiogram (ECG) is limited in detecting
short-lasting or minor myocardial ischemia. In comparison, intracoronary ECG (icECG) is more
time- and space-sensitive in detecting myocardial ischemia, the latter being due to its close
vicinity to the myocardial region of interest. It can be easily obtained by attaching an
alligator clamp to a coronary guidewire.
Based on the sensitivity of the icECG, several clinical trials have assessed the value of
icECG to guide PCI, and rated it useful to predict post-procedural myocardial injury.
The investigators research group performed a trial to determine the diagnostic accuracy of
icECG ST-segment shift during pharmacologic inotropic stress in assessing functional coronary
lesion severity versus structural stenosis severity as obtained by quantitative coronary
angiography in % diameter narrowing (%S by QCA), and versus other functional hemodynamic
indices (FFR, instantaneous wave-free ratio (iFR)). IcECG ST-segment shift showed a
significant correlation with all established parameters.
Evaluation of icECG required the development of a specific software algorithm, which robustly
determines quantitative icECG ST-segment shift in every single heartbeat. The validation
analysis of the algorithm took place in an offline setting and demonstrated an excellent
correlation as compared to the results of ECG experts (r2 = 0.932; p<0.001).
The development of this fully autonomous icECG analyzing algorithm was set up on an existing
ECG software, denoted as "EsoLive", developed at the Institute for Medical Engineering and
Medical Informatics, University of Applied Sciences and Arts Northwestern Switzerland. In
short, the algorithm starts with a baseline wander extraction method related to Kalman
filtering, then sets the initial points for an "edge", i.e., J-point, before, it processes in
a similar way the isoelectric line level. Quantitative time as well as voltage measurements
of those two points allow the calculation of the icECG ST-segment shift for each single QRS
complex.
This study evaluates a new diagnostic approach based on icECG ST-segment shift remission
time, denoted as τ-icECG (τ=tau, i.e., the remission half-time fitted by an exponential
function to the disappearing ST-segment shift), to be used for PCI guidance.
