Different Phases Of Cardiac Cycle Research Articles

Abstract 11835: Different Dynamic Luminal Compression of Intramural Segment During Cardiac Cycle in Anomalous Aortic Origin of Coronary Arteries Revealed by Ivus Gated Sequences

Introduction: Anomalous Aortic Origin of Coronary Artery (AAOCA) with intramural (IM) segment is associated with risk of sudden cardiac death (SCD). The pathogenic mechanism is believed to be the IM compression caused by the aorta expansion during effort. However, the IM compression occurrence and magnitude during the cardiac cycle remain unknown. Hypothesis: We hypothesized that the IM segment is subjected to dynamic compression during different phases of cardiac cycle with a luminal area and roundness smaller in systole than in end-diastole. Methods: Lumen dynamics was derived from IVUS pullbacks of N=35 AAOCA (N=23 with IM tract) after retrospective image-based gating to identify cardiac cycles. The cyclic change of area (A) and roundness (R=minimum/maximum lumen axis) of ostial, distal IM, and extramural (EM) tracts were described after manual lumen segmentation. The systolic phase was identified, in each patient, by estimating normal PQ and QT intervals from image-based gating. Results are presented with median and interquartile range. One-tailed Wilcoxon signed-rank test (p<0.025) assessed differences between systolic and diastolic phases in each tract. Results: A systolic reduction of roundness was observed in ostium [R systole = 0.5 (0.2), R diastole = 0.6 (0.3), flattening: -7% (10), p=0.01] and distal IM segment [R systole = 0.7 (0.2), R diastole = 0.8 (0.2), flattening: -6% (16), p=0.004]. No-IM segments showed normal behaviour and remained circular during the entire cardiac cycle. The distal IM had an area reduction during systole [A systole = 8.3 (2.3) mm 2 , A diastole = 8.1 (2.9) mm 2 , narrowing: -4% (11), p=0.009] that was not observed in all other segments (Figure 1). Conclusion: AAOCA with IM segment has pathological dynamic compression mainly in systole. Studying AAOCA behaviour with IVUS during the cardiac cycle may help to evaluate and quantify the severity of the narrowing.

Time series clustering of left atrial strain curves for risk stratification in the general population

Abstract Objective Currently, only the peak reservoir left atrial (LA) strain has been in use while a huge amount of useful information during different phases of cardiac cycle has been ignored. In this study, therefore, we tested the hypothesis that an unsupervised time series analysis utilizing the whole LA deformation curves will identify distinct clusters associated to risk factors and improve cardiovascular (CV) risk prediction over the traditionally used covariables in the general population. Design and method We prospectively studied 929 community-dwelling individuals (mean age, 51.6 years; 52.9% women), in whom we acquired clinical and echocardiographic data including LA strain traces at baseline and collected cardiac events on average 7.2 years later. We employed two unsupervised time series techniques such as Self-Organizing map and Variational Autoencoder (VAE) with Convolutional Neural Network as building block to cluster spatiotemporal patterns of LA strain curves. Clinical characteristics and cardiac outcome were used to evaluate the validity of the clusters (k). Results According to the quantization error value for every k, the optimal number of clusters was 5 for applied methods. Figure 1 (left panel) illustrates the centroids of the clusters using the proposed VAE network. The first three clusters had differences in sex distribution and heart rate, but had similar low CV risk profiles. On the other hand, cluster 5 had the worst CV risk factors combination, and higher prevalence of left ventricular remodelling and diastolic dysfunction (ie, lowest e' velocity and highest E/e') compared to other clusters. We also observed an increase in the risk for incidence of adverse events between cluster 5 and other clusters (Figure 1, right panel). After adjustment for traditional risk factors, cluster 5 had the highest risk of cardiac events as compared to cluster 1, 2 and 3 (HR: 1.36; 95% CI: 1.10–1.69); P=0.0046). Conclusion Unsupervised Machine/Deep Learning algorithms employed on time series LA strain curves identifies clinically meaningful clusters of LA deformation, and provides incremental prognostic information over traditional risk stratification. Funding Acknowledgement Type of funding sources: Public Institution(s). Main funding source(s): KU Leuven

Warm, but not hypoxic acclimation, prolongs ventricular diastole and decreases the protein level of Na+/Ca2+ exchanger to enhance cardiac thermal tolerance in European sea bass

One of the physiological mechanisms that can limit the fish's ability to face hypoxia or elevated temperature, is maximal cardiac performance. Yet, few studies have measured how cardiac electrical activity and associated calcium cycling proteins change with acclimation to those environmental stressors. To examine this, we acclimated European sea bass for 6 weeks to three experimental conditions: a seasonal average temperature in normoxia (16 °C; 100% air sat.), an elevated temperature in normoxia (25 °C; 100% air sat.) and a seasonal average temperature in hypoxia (16 °C; 50% air sat.). Following each acclimation, the electrocardiogram was measured to assess how acclimation affected the different phases of cardiac cycle, the maximal heart rate (fHmax) and cardiac thermal performance during an acute increase of temperature. Whereas warm acclimation prolonged especially the diastolic phase of the ventricular contraction, reduced the fHmax and increased the cardiac arrhythmia temperature (TARR), hypoxic acclimation was without effect on these functional indices. We measured the level of two key proteins involved with cellular relaxation of cardiomyocytes, i.e. sarco(endo)plasmic reticulum Ca2+-ATPase (SERCA) and Na+/Ca2+ exchanger (NCX). Warm acclimation reduced protein level of both NCX and SERCA and hypoxic acclimation reduced SERCA protein levels without affecting NCX. The changes in ventricular NCX level correlated with the observed changes in diastole duration and fHmax as well as TARR. Our results shed new light on mechanisms of cardiac plasticity to environmental stressors and suggest that NCX might be involved with the observed functional changes, yet future studies should also measure its electrophysiological activity.

TIME SERIES CLUSTERING OF LEFT ATRIAL STRAIN CURVES FOR RISK STRATIFICATION IN THE GENERAL POPULATION

Objective: Currently, only the peak reservoir left atrial (LA) strain has been in use while a huge amount of useful information during different phases of cardiac cycle has been ignored. In this study, therefore, we tested the hypothesis that an unsupervised time series analysis utilizing the whole LA deformation curves will identify distinct clusters associated to risk factors and improve cardiovascular (CV) risk prediction over the traditionally used covariables in the general population. Design and method: We prospectively studied 929 community-dwelling individuals (mean age, 51.6 years; 52.9% women), in whom we acquired clinical and echocardiographic data including LA strain traces at baseline and collected cardiac events on average 7.2 years later. We employed two unsupervised time series techniques such as Self-Organizing map and Variational Autoencoder with Convolutional Neural Network as building block to cluster spatiotemporal patterns of LA strain curves. Clinical characteristics and cardiac outcome were used to evaluate the validity of the clusters (k). Results: According to the quantization error value for every k, the optimal number of clusters was 5 for applied methods. Overall, both methods agreed with respect to cluster assignment. Figure (left panel) presents centroid LA strain curves which represent each cluster. The first three clusters had differences in sex distribution and heart rate, but had similar low CV risk profiles. On the other hand, cluster 5 had the worst CV risk factors combination, and higher prevalence of left ventricular remodelling and diastolic dysfunction (ie, lowest e’ velocity and highest E/e’) compared to other clusters. We also observed an increase in the risk for incidence of adverse events between cluster 5 and other clusters (Figure, right panel). After adjustment for traditional risk factors, cluster 5 had the highest risk of cardiac events as compared to cluster 1, 2 and 3 (HR: 1.34; 95%CI: 1.05–1.73); P = 0.020). Conclusions: Unsupervised Machine/Deep Learning algorithms employed on time series LA strain curves identifies clinically meaningful clusters of LA deformation, and provides incremental prognostic information over traditional risk stratification.

Application of Perfusion Single Photon Emission Computed Tomography of the Myocardium in Pain-Free Myocardial Ischemia

This literature review provides data on the use of single-photon emission computed tomography of myocardium in silent myocardial ischemia. The presence of silent myocardial ischemia increases the risk of cardiovascular complications several times and may be the first manifestation of coronary heart disease. Assessing the state of morphofunctional processes in the myocardium is the main goal of diagnostic imaging using singlephoton emission computed tomography of the myocardium. This allows to get three-dimensional image of left ventricle with information about distribution of perfusion volume across myocardium, makes it possible to more accurately differentiate such condition as silent myocardial ischemia. Conducting single-photon emission computed tomography in ECG synchronization mode allows you to visualize the kinetics of the myocardial walls in different phases of the cardiac cycle and thereby simultaneously assess the functional state of the left ventricular myocardium. Indicators of contractile function of the left ventricular myocardium in areas of transient hypoperfusion can be predictors of cardiac events after myocardial infarction and independent predictors of perioperative cardiac events in patients undergoing cardiac surgery. Performing single-photon emission computed tomography in ECG-synchronization mode allows visualizing kinetics of myocardial walls in different phases of cardiac cycle and thereby simultaneously assessing functional state of left ventricle myocardium. In combination with physical exercise and pharmacological tests, it helps to identify coronary stenosis among patients with silent myocardial ischemia. Perfusion single-photon emission computed tomography of myocardium is a necessary tool for stratification and assessment of prognosis of cardiac diseases in asymptomatic patients.

A novel formulation for the study of the ascending aortic fluid dynamics with in vivo data

Numerical simulations to evaluate thoracic aortic hemodynamics include a computational fluid dynamic (CFD) approach or fluid-structure interaction (FSI) approach. While CFD neglects the arterial deformation along the cardiac cycle by applying a rigid wall simplification, on the other side the FSI simulation requires a lot of assumptions for the material properties definition and high computational costs. The aim of this study is to investigate the feasibility of a new strategy, based on Radial Basis Functions (RBF) mesh morphing technique and transient simulations, able to introduce the patient-specific changes in aortic geometry during the cardiac cycle. Starting from medical images, aorta models at different phases of cardiac cycle were reconstructed and a transient shape deformation was obtained by proper activating incremental RBF solutions during the simulation process. The results, in terms of main hemodynamic parameters, were compared with two performed CFD simulations for the aortic model at minimum and maximum volume. Our implemented strategy copes the actual arterial variation during cardiac cycle with high accuracy, capturing the impact of geometrical variations on fluid dynamics, overcoming the complexity of a standard FSI approach.

Application of vector flow mapping technique in the assessment of left intraventricular pressure gradients in heart failure patients

Objective To evaluate the changes of intraventricular pressure differences (IVPDs) and intraventricular pressure gradients (IVPGs) in different phases of cardiac cycle in patients with heart failure(HF) patients by relative pressure imaging based on vector flow imaging(VFM). Methods Forty-nine HF patients with left ventricular ejection fraction (LVEF) lower than 0.50 hospitalized in Qilu Hospital of Shandong University from November 2018 to January 2019, including thirty-three patients with HF with reduced ejection fraction (HFrEF group) and fifteen patients with midrange ejection fraction (HFmrEF group), and forty-three controls were enrolled in this study. Clinical data and echocardiographic images were collected and the conventional left ventricular diameter, mass, volume, and systolic and diastolic function parameters were measured. IVPDs and IVPGs during isovolemic systole (IC), rapid ejection (RE), isovolemic diastole (IR), rapid filling (RF) and atrial systole (AC) phases were obtained by the VFM technique. The changes of IVPDs and IVPGs in different phases between the HF and control groups, and their correlations with conventional ultrasound parameters were analyzed. Results IVPDs and IVPGs in heart failure group were significantly reduced compared with the control group especially in isovolumic relaxation phase(all P<0.001). IVPDs and IVPGs showed a decreasing trend in the control group, HFmrEF group and the HFrEF group(P<0.001). IVPDs and IVPGs were correlated with LVID, LVMI, ESV, LVEF, GLS and E/e′ (all P<0.01), among which IVPD-IR and IVPG-IR were best correlated. IVPD-IR and IVPG-IR had excellent diagnostic efficacy for HF patients with LVEF<0.5, with cut-off values of <0.73 mmHg (AUC=0.915, P<0.001) and <0.103 mmHg/cm (AUC=0.932, P<0.001), respectively. Conclusions Early diastolic hemodynamics are severely impaired when systolic function declines.IVPG-IR, as a marker of left ventricular diastolic function, significantly correlates with left ventricular systolic function, and can be used as a potential indicator for assessing left ventricular systolic and diastolic function in patients with heart failure and identifying patients with heart failure. Key words: Vector flow imaging; Relative pressure imaging; Intraventricular pressure gradients; Heart failure

Application value of vector flow mapping in assessing the degrees of coronary artery stenosis

Objective To quantify the left ventricular flow field characteristics of different phases of cardiac cycle in patients with different degrees of coronary artery stenosis by using vector flow mapping (VFM), and explore the value of quantitative parameters of VFM in diagnosis of degrees of coronary artery stenosis in patients with coronary heart disease. Methods Eighty-four patients with coronary artery stenosis showed by coronary angiography served as case group. According to the results of coronary angiography, all the patients of case group were divided into 3 groups: mild stenosis group, moderate stenosis group and severe stenosis group. Forty-five healthy adult volunteers were selected as control group. The quantitative parameters, including average energy loss (EL-base, EL-mid, EL-apex) and circulation (vortex area, circulation), were measured in the different periods of VFM mode. The difference of parameters were evaluated between case group and control group during different periods. E/e′ was derived via dual-Doppler imaging technology and correlation was analyzed between aEL, circulation, E/e′(L) and E/e′(S), separately. ROC curve was used to analyze aEL in severe stenosis group, and to evaluate the diagnostic efficacy of aEL in different cardiac cycles. Results ①Compared with the control group, aEL in global and regional segment of left ventricle in the severe stenosis group were significantly increased during isovolumetric relaxation period, reduced filling period, atrial systolic phase and isovolumic contraction period (all P<0.05). And the aEL in global and regional segment of left ventricular in the moderate stenosis group were significantly increased during reduced filling period, atrial systolic phase and isovolumic contraction period (all P<0.05). And the aEL in middle segment of left ventricular in the mild stenosis group was significantly increased during reduced filling period (P<0.05). ②Compared with the control group, the vortex area and circulation intensity in left ventricular of the severe stenosis group were significantly increased during isovolumetric relaxation period, reduced filling period, atrial systolic phase and isovolumic contraction period(P<0.05). ③In case group, there were positive correlations between aEL with E/e′(L) or E/e′(S) at global and regional segment of rapid filling phase and atrial systolic phase. And there were positive correlations between the vortex area or circulation intensity and E/e′(L) or E/e′(S) during reduced filling period and atrial systolic phase. Conclusions VFM can effectively evaluate the flow field characteristics of left ventricle in patients with coronary heart disease. The quantitative parameters of VFM can reflect the extent of coronary artery stenosis in some extent. Key words: Vector flow mapping; Coronary stenosis; Energy loss; Circulation

The Role of Left Atrium

Left atrium (LA) contributes 20-30% of cardiac output. LA volume and function measured by 2D biplane area length and real-time 3D echocardiography have been well-validated and widely used. LA function consists of 3 components, including reservoir, conduit, and active contractile phases. The most frequently used echocardiographic method for evaluation of phasic function of LA is volumetric method. LA volume measured by biplane area-length method and corrected by body surface area is a useful index for studying LA remodeling, and early LA remodeling has been proven to have prognostic significance in heart failure after myocardial infarction. Phasic changes of LA volume can be measured in different phases of cardiac cycle. Volumetric measurements are useful in evaluation of LA, however, volumetric changes can not reflect changes of the LA wall itself. Tissue Doppler imaging has been applied for the assessment of cardiac function, including atrial function. Atrial deformation evaluated by tissue Doppler derived strain or strain rate imaging can be used for assessment of LA wall directly. Newly developed speckle tracking echocardiography is useful in assessment of left ventricular strain and strain rate. This non-Doppler two-dimensional strain imaging avoids effects of Doppler angle and ventricular tethering. Speckle tracking echocardiography was recently used for assessment of LA function after resynchronization therapy. The feasibility of LA longitudinal strain and strain rate measured by speckle tracking echocardiography has been verified in healthy subjects, and adequate tracking can be performed in 94% of subjects or in 97% of segments. Early changes of LA function can be documented by speckle tracking echocardiography. We have found the phasic LA function changed in untreated hypertension subjects and correlated with left ventricular diastolic function. LA strain also has prognostic implications such in primary mitral regurgitation or in atrial fibrillation.

Reproducibility of serial optical coherence tomography measurements for lumen area and plaque components in humans (The CLI-VAR [Centro per la Lotta Contro l'Infarto-variability] II study).

Frequency-domain optical coherence tomography (FD-OCT) is a promising intracoronary imaging technique to study atherosclerosis. Indeed, its unprecedented spatial resolution allows the assessment of fibrous cap thickness, lipid pool and features of plaque vulnerability. Aim of this study was to determine the reproducibility of the in vivo FD-OCT measurements of lumen area and plaque components in serial studies. Twenty-six patients undergoing FD-OCT assessment of intermediate lesion during coronary angiography were included in this study. FD-OCT pullbacks were acquired twice from the same coronary segment at interval of 5 min without additional intervention and analyzed off-line at an independent imaging core laboratory. Lumen diameter (LD), lumen area (LA), fibrous cap (FC) thickness and lipid pool (LP) arc extension measurements were compared in 440 matched frames. Both the per-segment and per-frame analyses showed excellent correlation coefficients for the inter-pullback comparisons for all parameters explored (R > 0.95 and p < 0.001 in all cases). Accordingly, the Bland-Altman estimates of bias showed non-significant differences in the inter-pullback comparisons at all levels. Per-frame analysis showed a slightly variations of LA in 45.8% of cases with changes greater than 2% likely related to different phases of cardiac cycle. Nevertheless, nor FC thickness or circumferential arc of LP were affected by LA changes during serial FD-OCT acquisition. This study showed an excellent reproducibility of lumen and plaque component measurements obtained with FD-OCT in vivo. Thus, this intracoronary imaging technique could be used to assess atherosclerosis progression and describe accurate plaque evolution in repeated serial studies.

A Case of Right Atrial Mass

Not available DOI: http://dx.doi.org/10.3329/cardio.v5i1.12284 Cardiovasc. j. 2012; 5(1): 123-124

Cardiovascular magnetic resonance imaging in assessment of intracaval and intracardiac extension of renal cell carcinoma

About 1 in 5 patients with renal cell carcinoma have intravascular tumoral extension at presentation. Level of tumoral extension within inferior vena cava determines surgical approach, with higher extension requiring cardiopulmonary bypass. Tumoral invasion of inferior vena caval wall is associated with poor prognosis. We evaluated accuracy of magnetic resonance imaging (MRI) in assessing level of intravascular extension of renal cell carcinoma and predicting vessel wall invasion. MRIs and surgical database were reviewed from January 1999 to December 2008. Sixty-four patients with suspected intravascular extension of renal cell carcinoma underwent MRI. Forty-one underwent curative or palliative surgery at our institution and were included in final analysis. MRI scans were reviewed to determine intravascular extension and tumoral adherence to the vessel wall, as assessed by circumferential flow around the intravascular tumor and its mobility during different phases of cardiac cycle. MRI findings were correlated with surgical findings to assess accuracy. There was 87.8% agreement (P<.001; κ=0.82) between MRI and surgical findings regarding level of intravascular extension of tumor. MRI was highly sensitive and specific (93%) in assessing supradiaphragmatic extension (negative predictive value, 96%). Depending on sign used, sensitivities and negative predictive values in assessing tumoral adherence to vessel wall ranged from 86% to 95% and 81% to 91%, respectively. MRI is highly accurate in staging intravascular and intracardiac extension, aiding in accurate preoperative surgical planning. MRI may help determine prognosis of renal cell carcinoma by accurately assessing tumoral adherence to the vessel wall.

낭상 뇌동맥류 혈류유동에서 비뉴우토니안 유체 모델의 영향

The importance of shear thinning non-Newtonian blood rheology on the hemodynamic characteristics of idealized cerebral saccular aneurysms were investigated by carrying out CFD simulations assuming two different non-Newtonian rheology models (Carreau and Ballyk models). To explore effects of vessel curvature, a straight and a curved vessel geometry were considered. The wall shear stress(WSS), relative residence time(RRT) and velocity distribution were compared at the different phases of cardiac cycle. As expected, blood entered the aneurysm at the distal neck and created large vortex in both aneurysms, but with higher momentum on the curved vessel. Hemodynamic characteristics such as WSS, and RRT exhibited only minor effects by choice of different rheological models although Ballyk model produced relatively higher effects. We conclude that the assumption of Newtonian fluid is reasonable for studies aimed at quantifying the hemodynamic characteristics, in particular, WSS-based parameters, considering the current accuracy level of medical image of cerebral aneurysm.

Frame rate requirement for tissue Doppler imaging in different phases of cardiac cycle: radial and longitudinal functions

Tissue Doppler imaging (TDI) has been suggested for quantitative analysis of regional myocardial function. Myocardial movement included different mechanical phases with different duration and tissue velocity profiles need to high sampling rate in the acquisition of tissue velocity imaging for phases with shorter duration. The aim of this study is determining of frame rate requirement for myocardial tissue velocity imaging for longitudinal and radial functions separately. Tissue velocity imaging recorded from 29 healthy volunteers by use of the apical and para-sternal views. Off-line analysis performed for extracting tissue velocity profiles of the myocardial longitudinal and radial functions. The frequency and subsequently the frame rate calculated separately for all LV segments during two consequent cardiac cycles. Segmental distribution of the time intervals measured in all cardiac phases and the minimum frame rate requirement calculated for each segment. We found significant differences between radial and longitudinal functions (P < 0.001) except early diastolic phases. The presented normal frame rate values for LV segments may useful for accurate studies of myocardial longitudinal and radial functions in different cardiac phases. We conclude that data sampling at a rate of at least 105 and 118 frames per second need for longitudinal and radial functions respectively.

Morpho-functional assessment of interatrial septum: a transesophageal echocardiographic study

Background: Despite the increasing number of reports on lipomatous hypertrophy of interatrial septum, a standardization of measurement of the dimensions of the interatrial septum (IAS) in the different phases of cardiac cycle has not been reported. Moreover, no data on modification of thickness with age and in specific cardiac diseases are available. Objective: Our purpose was to study whether the changes of thickness and thinning of IAS may be related to age, left atrial dimension, cardiac cycle and different cardiac diseases. Methods: 248 patients (mean age 52.7 ± 19.9 years) underwent transthoracic (TTE) and transesophageal (TEE) echocardiography. IAS was measured at the constant regions anterior and posterior to the fossa ovalis. IAS thickness (tk), thinning (th) and % thinning (% th) were measured. Results: IAS thickness ranged from 4 to 13 mm at the time of ventricular end-systolic phase (mean 6.7 ± 1.9 mm) and from 6 to 16 mm at the time of atrial systole (mean 9.9 ± 1.8 mm); significant statistical difference between these values was found ( P < 0.01). IAS thinning ranged from 1 to 7 mm (mean 3.42 ± 1.8) while % IAS thinning from 18 to 76% (mean 36.53 ± 16.36%). Statistical analysis showed a significant positive correlation between age and ventricular end-systolic thickness and atrial systolic thickness and thinning. An insignificant correlation was found between age and % IAS thinning and between left atrial dimension and IAS tk and th. Conclusions: Our results demonstrate that IAS thickness increases by age; no correlation exists between IAS thinning and age. There is no difference between IAS thickness and thinning in patients with or without cardiac disease. We believe that the thickness of IAS can be considered hypertrophic only if it exceeds the value of 15 mm during both ventricular end-systolic and atrial systolic phases of the cardiac cycle. IAS thickness and thinning might be an additional parameter to evaluate systolic atrial function particulary with regard to maintenance of synus rhythm after conversion from atrial fibrillation as well as to better understand its role in determining the filling of ventricles in different clinical conditions.

Cardiac phase-related variability of border detection or densitometric quantitation of postangioplasty lumens

We applied an automated computer program capable of simultaneous geometric (through border detection) and densitometric quantitation of digital angiograms for evaluation of the results of percutaneous transluminal coronary angioplasty (PTCA) in different phases of the same cardiac cycle. Digital subtraction coronary angiograms (DSA) of 28 patients who had undergone PTCA to a total of 30 lesions, were analyzed in diastole, in systole, and in the middle of the cardiac cycle to test the variability in coronary quantitation resulting from random frame selection relative to cardiac phase. Before PTCA there was a low degree of variation between measurements obtained from the same lesion in different phases of the cardiac cycle, in both geometric (coefficient of variation between cardiac phases = 4.2%) and densitometric (coefficient of variation between cardiac phases = 5.1%) quantitation. After PTCA, however, there was a wider variation of values in different cardiac phases, which predominated in the densitometric measurements (coefficient of variation between cardiac phases = 33.6%, compared to 20.6% for geometric measurements). There was less agreement between different post-PTCA phases in densitometry, and discrepancies as large as 47% could occur in densitometric evaluation of the stenotic areas when different phases of the cycle were used. We conclude that border detection or densitometric quantitation of the postangioplasty lumens is subject to greater variation resulting from random frame selection relative to cardiac phase, as compared to preangioplasty assessment. This variation predominates in densitometric quantitation, which seems to be dependent not only on the radiographic projection but also on the cardiac phase. The usefulness of densitometric techniques for the evaluation of PTCA results appears to be questionable.