Automated myocardial perfusion from coronary X-ray angiography

The purpose of our study is the evaluation of an algorithm to determine the physiological relevance of a coronary\ud lesion as seen in a coronary angiogram. The aim is to extract as much as possible information from a standard\ud coronary angiogram to decide if an abnormality, percentage of stenosis, as seen in the angiogram, results in\ud physiological impairment of the blood supply of the region nourished by the coronary artery. Coronary angiography,\ud still the golden standard, is used to determine the cause of angina pectoris based on the demonstration\ud of an important stenose in a coronary artery. Dimensions of a lesion such as length and percentage of narrowing\ud can at present easily be calculated by using an automatic computer algorithm such as Quantitative Coronary\ud Angiography (QCA) techniques resulting in just anatomical information ignoring the physiological relevance of\ud the lesion. In our study we analyze myocardial perfusion images in standard coronary angiograms in rest and\ud in artificial hyperemic phases, using a drug e.g. papaverine intracoronary. Setting a Region of Interest (ROI) in\ud the angiogram without overlying major vessels makes it possible to calculate contrast differences as a function of\ud time, so called time-density curves, in the basal and hyperemic phases. In minimizing motion artifacts, end diastolic\ud images are selected ECG based in basal and hyperemic phase in an identical ROI in the same angiographic\ud projection. The development of new algorithms for calculating differences in blood supply in the region as set\ud are presented together with the results of a small clinical case study using the standard angiographic procedur

CAD of myocardial perfusion

Our purpose is in the automated evaluation of the physiological relevance of lesions in coronary angiograms. We aim to extract as much as possible quantitative information about the physiological condition of the heart from standard angiographic image sequences. Coronary angiography is still the gold standard for evaluating and diagnosing coronary abnormalities as it is able to locate precisely the coronary artery lesions. The dimensions of the stenosis can be assessed nowadays successfully with image processing based Quantitative Coronary Angiography (QCA) techniques. Our purpose is to assess the clinical relevance of the pertinent stenosis. We therefore analyze the myocardial perfusion as revealed in standard angiographic image sequences. In a Region-of-Interest (ROI) on the angiogram (without an overlaying major blood vessel) the contrast is measured as a function of time (the so-called time-density curve). The required hyperemic state of exercise is induced artificially by the injection of a vasodilator drug e.g. papaverine. In order to minimize motion artifacts we select based on the recorded ECG signal end-diastolic images in both a basal and a hyperemic run in the same projection to position the ROI. We present the development of the algorithms together with results of a small study of 20 patients which have been catheterized following the standard protocol

On the Assessment of Image Compression Quality By Means of Quantitative Coronary Angiography

Many techniques for image compression do exist and are well described in the literature. Lossless image compression is for digital coronary angiograms limited to compression ratios in the order of 3--4. The purpose of this work is about the assessment of the diagnostic image quality of lossy compressed coronary angiograms by means of Quantitative Coronary Angiography (QCA). We measure in the compressed images the diameter of the vessel at several places as a function of the compression ratio and compare this with the original image. The set of representative images (512 by 512 pixels at 8 bits/pixel) is compressed with the ratios 4, 8, 12 and 16. The selected compression algorithms are JPEG, Lapped Orthogonal Transform (LOT) and Modified Fast Lapped Transform (MFLT). The obtained quantitative diameter values start to deviate at images representations down at 0.5 bit per pixel with the JPEG giving the greatest differences (typ. ? 5%). The results of LOT and MFLT are performing better wi..

Coronary Artery Diameter Variations due to Pulse Flow Propagation

Information about local diameter variations as a response to the pulse flow in the human coronary arteries may indicate the development of artherosclerosis before this can be seen as a stenosis on coronary angiograms. This paper describes the design of an image processing tool to measure this diameter variation from a sequence of digital coronary angiograms. If a blood vessel reponds less elastically to the pulse flow, this may be an indication of artherosclerosis in an early stage. We have developed an image analysis and processing algorithm which is able after vessel segment selection by the user, to calculate automatically the vessel diameter variations from a standard sequence of digital angiograms. Several problems are treated. The periodic motion of the vessel segment in the consecutive frames is taken into account by tracking the vessel segment using a 2-dimensional logarithmic search to find the minimum in the mean absolute distance. A robust artery tracing algorithm has been i..

Heart rate control via vagus nerve stimulation

Objectives: There is ample and well-established evidence that direct electrical stimulation of the vagus nerve can change heart rate in animals and humans. Since tachyarrhythmias cannot always be controlled through medication, we sought, in this pilot study, to elucidate whether a clinical implantable lead system that is used in cervical vagus nerve stimulation therapy (VNS therapy) also can be used for control of heart rate, and tachycardia in particular. - \ud Materials and Methods: Experiments were carried out in three pigs (weight 21–26 kg) under general anesthesia. The right and left vagus nerves in the neck region were exposed by dissection, and bipolar, multiturn, helical, silicone leads were wrapped around the vagus nerves. Stimulation was applied by an external device with multivariable settings: frequency 10–100 Hz, pulse duration 100–700 µsec; delay 0–0.5 msec; current 0.5–14 mA. Measurements were performed under normal sinus rhythm (RR-interval 501 ± 30 msec) and during isoprenaline-induced tachycardia (RR-interval 284 ± 11 msec). - \ud Results: VNS, under optimal pacing conditions (100 Hz; 5 mA; 0.2 msec; 70 msec delay), in an electrocardiogram-triggered (ECG-triggered) pacing mode, increased RR-intervals by approximately 40%, irrespective of the duration of the RR-interval preceding VNS. The maximum effect on heart rate was established within approximately 5 sec after the onset of stimulation and was reversible and reproducible. No differences were found between stimulation of the right or left vagus nerve. - \ud Conclusion: VNS can be used effectively and rapidly to decrease heart rate, in acute settings, when connected to an external pacing system. Future devices that are fully implantable may be used for nonpharmacological treatment of illnesses in which tachycardia results in deterioration of cardiac function

Sustained benefit 20 years after reperfusion therapy in acute myocardial infarction

ObjectivesThe goal of this research was to clarify whether the benefit of reperfusion therapy for myocardial infarction was sustained long-term and to assess the gain in life expectancy by reperfusion therapy.BackgroundReperfusion therapy in acute myocardial infarction reduces infarct size and increases hospital survival.MethodsWe analyzed the 20-year outcome of 533 patients (mean age 56 years; 82% men) who were randomized to either reperfusion therapy or conventional therapy during the years 1981 to 1985.ResultsMean follow-up was 21 years (range 19 to 23 years). At follow-up, 101 patients (36%) of the 269 patients allocated to reperfusion treatment and only 71 patients (26%) of the 264 conventionally treated patients were alive (p = 0.02). The cumulative 10-, 15-, and 20-year survival rates were 69%, 48%, and 37% after reperfusion therapy and 59%, 38%, and 27% in the control group, respectively (p = 0.005). Life expectancy of the reperfusion group was 15.2 years versus 12.4 years in the conventionally treated group (p < 0.0001). Myocardial re-infarction and subsequent coronary interventions were more frequent after reperfusion therapy, particularly during the first year. In multivariable analysis, reperfusion therapy was an important independent predictor of lower mortality at long-term follow-up (hazard ratio 0.7; 95% confidence interval 0.6 to 0.8). Other independent predictors of mortality were age, impaired left ventricular function, multivessel disease, infarct size, and inability to perform an exercise test at the time of discharge.ConclusionsThis is the first study demonstrating sustained (20-year) improved survival after reperfusion therapy. The gain in life expectancy was almost three years, representing about one-third of the life-years lost by myocardial infarction