Cardiac Respiratory Stress Test Can Quickly Detect
Significant Coronary Artery Disease
RSR test is simple and fast to perform in a doctor's
office without the need for significant expense and hardship
Jan. 19, 2010 – Testing a patient's cardiac
respiratory stress response (RSR) can quickly and accurately detect the
presence of significant coronary artery disease (S-CAD), according to
new research published in the current issue of Cardiovascular
Revascularization Medicine. The results found patients with S-CAD had a
significantly lower RSR compared to patients without (6.7% vs. 17.4%,
respectively) suggesting RSR is a strong indicator for the disease.
To determine cardiac respiratory stress response (RSR),
Washington Hospital Center researchers used a new innovative respiratory
stress test. The test uses a Pulse Oximeter (PPG) to measure blood flow
in the finger in response to paced breathing over a 90 second time
period. The PPG data are immediately captured and analyzed using a
proprietary algorithm that determines the RSR.
All findings were confirmed using Quantitative
Coronary Angiography (QCA). In comparison to QCA, the test results were
highly accurate, with a sensitivity and specificity of 86% and 81%,
respectively. No adverse events were reported.
"It is always challenging to detect significant
coronary artery disease in patients at the physician's office and often
required a physical stress test, including nuclear imaging and often
cardiac catheterization" said lead investigator Ron Waksman, MD,
Associate Director, Division of Cardiology, Washington Hospital Center
and professor of medicine (cardiology) at Georgetown University in
Washington DC.
"The RSR test is simple and fast to perform in a
doctor's office without the need for significant expense and hardship to
the patient, and the results of the study support its accuracy to detect
significant coronary artery disease. We believe it could be a useful
diagnostic option."
The test is not yet cleared for use in the US. The
safety and efficacy of the test compared to stress electrocardiography
in detecting S-CAD is currently the subject of the pivotal 1,000-patient
SCORE (Spirocor Coronary Outcome by Respiratory stress Examination)
study.
Dr. Waksman is a co-primary investigator of the
study, which is being conducted in over 25 cardiology clinics across the
US.
Study Methodology and Findings
In this prospective observational cohort study, the
RSR test was performed on 153 consecutive patients referred for coronary
angiography with symptoms or signs suggestive of CAD. The RSR tests were
conducted in a holding area of the catheterization laboratory by a
single examiner blinded to the patient's clinical data.
Coronary angiography was performed on all subjects
and analyzed by one cardiologist blinded to the subject's clinical data
and RSR using a validated QCA algorithm. In accordance with American
Heart Association guidelines, S-CAD was defined as at least a 70%
narrowing of at least 1 epicardial artery or at least a 50% narrowing of
the left main coronary artery.
A valid RSR was obtained in 150 patients (98%).
Thirty-six patients (24%) were found to have S-CAD, 31 had single-vessel
disease, and 5 had multi-vessel disease. The mean age of patients was
58.7, and the majority were male (67%).
The clinical characteristics of the 150 analyzed
patients were similar except for a higher rate of statin and
antiplatelet therapy in patients with S-CAD. The mean RSR was
significantly reduced in patients with S-CAD, regardless of age, gender,
the existence of risk factors, and medical treatment.
Using a receiver operating characteristic curve
analysis, the results suggest that an RSR of < 10.2% is a non-invasive
indicator of S-CAD, with a sensitivity and specificity of 86% and 81%,
respectively; positive and negative predictive values of 59% and 95%,
respectively; and positive and negative likelihood ratios of 4.46 and
0.17, respectively.
Additional multicenter, community-based studies
under varying clinical settings and patient populations are warranted to
rigorously assess the value of this test for the detection of S-CAD.
About the RSR Test
The proprietary respiratory stress test system
developed by SPIROCOR features a non-invasive PPG finger probe connected
to a computer with analyzing software residing on a central server,
accessed via the internet. The patient performs a controlled breathing
exercise which consists of inhaling and exhaling seven times. The PPG
signal is automatically captured and the data transmitted for analysis.
The RSR report is then automatically generated and made available on a
password secured website for the cardiologist to review and make a
decision regarding the next diagnostic and therapeutic step.
About Coronary Artery Disease (CAD)
Coronary artery disease is caused by a reduction of
blood flow to the heart due to a narrowing or blockage of the coronary
arteries. According to the American Heart Association, more than 13
million Americans suffer from CAD. It is the leading cause of death in
the US and costs the economy more than $142 billion annually. Cardiac
stress tests are the most common non-invasive testing methods used to
evaluate patients with suspected CAD, with approximately 20 million
stress tests performed annually in the US alone. Unfortunately, these
tests are often expensive, time consuming and can involve exposure to
ionizing radiation. As a result, they are not always available.
About SPIROCOR
SPIROCOR has advanced significant coronary artery
disease (S-CAD) diagnosis by developing an office based, effective,
low-cost, low-risk, non-invasive, functional diagnostic test assessing
cardiovascular respiratory response. The web based platform, via its
secure electronic access, enables cardiologists throughout the world to
evaluate and fast track the diagnosis and treatment of S-CAD.
The SPIROCOR system provides significant leverage
through global scalability of operation and control of intellectual
property with data being utilized to create new analyses and subgroup
optimizations supporting expanded diagnostic and monitoring
applications. SPIROCOR's headquarters, manufacturing and R&D facilities
are located in Israel. For more information, please visit
www.SPIROCOR.com.
