Hemodynamic evaluation in acute myocardial infarction

Bedside right heart catheterization in patients with acute myocardial infarction and hemodynamic dysfunction provides a rational basis for therapy aimed at maximizing cardiac performance and limiting infarct size. Readily performed and associated with minimal risk, this diagnostic approach is primarily indicated when myocardial infarction is associated with evidence of hemodynamic dysfunction. It affords precise information on cardiac performance and prognosis, allows identification of specific complications such as ventricular septal defect and acute mitral regurgitation, and is of critical importance in selection of therapy. Hemodynamic monitoring is also essential for safe, effective application of certain forms of treatment such as vasodilator therapy for the failing ventricle.

Myocardial contrast echocardiography in the perfusion imaging in coronary occlusion and reperfusion

The availability of myocardial contrast echocardiography (MCE) has potential for several applications in coronary diseases. Experimental studies have demonstrated a good correlation between measurements of myocardial blood flow and regional contrast intensity, and therefore capabilities of MCE in detecting myocardial ischemia during stress. Clinical studies must then demonstrate the value of such approaches in comparison with existing techniques such as stress echo and radionuclide imaging.

Eustachian valve endocarditis: a case series and analysis of the literature

Eustachian valve endocarditis (EVE) is a syndrome characterized by clinical signs and symptoms of right-sided infective endocarditis in association with an infective vegetation on the eustachian valve. EVE usually occurs without associated involvement of any other cardiac valves, and it is difficult to diagnose accurately by transthoracic echocardiography. Transesophageal echocardiography appears to be a more sensitive tool for the diagnosis of EVE, and it is recommended when a patient with typical signs of right-sided endocarditis has normal results on a transthoracic echocardiography study. In general, EVE responds well to conventional antibiotic therapy.

Accuracy and reproducibility of coronary flow rate assessment by real-time contrast echocardiography: in vitro and in vivo studies

Real-time myocardial contrast echo (MCE) provides the potential to assess myocardial blood flow from time-intensity refilling curves after high-energy bubble destruction. This study validated the accuracy of this approach and the effect of specific examination variables and instrument settings on results. The effects of examination depth and angle as well as dynamic range, pulse repetition frequency, and line density were assessed with the use of in vitro incremental flow rates produced in an in vitro tissue phantom. In vivo recordings of real-time imaging with an infusion of a contrast agent (Optison) were obtained in 7 open-chest dogs with graded left anterior descending artery stenosis at baseline and during adenosine hyperemia, and were compared with flow probe measurements. After bubble destruction, time-intensity data were fitted to an exponential function, and the rate of intensity increase (b) and peak plateau intensity (A) were derived from refilling curves. In vivo real-time values for b, but not A, correlated closely with flow probe measures (r = 0.93). A similar correlation for b was observed in vitro (r = 0.98). The correlation between flow rate and b was influenced by several examination variables, including depth, angle, and instrument settings. Real-time MCE provides accurate quantification of coronary flow by assessing the rate of microbubble refilling. However, this parameter may be affected by several examination and instrument variables. Therefore, real-time MCE refilling measures are best applied by comparing baseline values with those of stress studies.

Aortic intramural hematoma: an increasingly recognized and potentially fatal entity

Aortic intramural hematoma (IMH) is related to but is pathologically distinct from aortic dissection. In this potentially lethal entity, there is hemorrhage into the aortic media in the absence of an intimal tear. Although intimal disruption is not present, the prognosis is similar to that of classic aortic dissection; therefore, early diagnosis is critical. In this review, symptoms and prognosis of aortic IMH are discussed, as well as current diagnostic techniques and therapy.

Comparison of real-time and intermittent triggered myocardial contrast echocardiography for quantification of coronary stenosis severity and transmural perfusion gradient

BACKGROUND

Both intermittent triggered and real-time myocardial contrast echocardiography (MCE) have been proposed to detect impaired myocardial perfusion. We compared the ability of these 2 methods to quantify altered myocardial blood flow (MBF) and transmural distribution of MBF produced by graded coronary stenoses.

METHODS AND RESULTS

In 8 open-chest dogs, we created 4 graded left anterior descending coronary artery (LAD) stenoses: 3 levels of reduced adenosine hyperemia (non-flow-limiting at rest) and 1 grade of flow-limiting at rest. Real-time MCE was performed with SonoVue infusion using low-energy power pulse inversion (ATL) imaging, whereas ECG-gated intermittent triggered imaging used high energy at pulsing intervals from 1:1 to 1:10. LAD signal intensity (SI) was plotted versus time by real-time MCE and versus pulsing intervals by triggered MCE and was fitted to a 1-exponential function to obtain plateau SI (A) and the rate of SI rise (b). Visual detection of decreased opacification was equivalent by triggered and real-time MCE. Fluorescent microsphere-derived MBF ratio in LAD/left circumflex artery beds demonstrated close correlation with both real-time imaging (b, r=0.79; Axb, r=0.81) and triggered imaging (b, r=0.78; Axb, r=0.80). The endocardial/epicardial ratio of MBF in the LAD bed demonstrated closer correlation with the endocardial/epicardial ratios of b (r=0.71) and Axb (r=0.67) obtained by real-time than triggered imaging (b, r=0.42; Axb, r=0.52).

CONCLUSIONS

Real-time and triggered MCE are equivalent in their ability to identify coronary stenosis and quantify altered MBF.

Comparative value of dobutamine and adenosine stress in the detection of coronary stenosis with myocardial contrast echocardiography

BACKGROUND

Controversy continues as to whether adenosine or dobutamine is the superior pharmacological stress agent for myocardial contrast echocardiography (MCE).

METHODS AND RESULTS

We compared real-time MCE refilling curves and wall thickening during adenosine and dobutamine stress in 14 open-chest dogs with left anterior descending and left circumflex coronary artery stenoses that reduced hyperemia by 40% to 60% and 70% to 90% (mild and severe non-flow-limiting stenosis, NFLS) and resting flow by 10% to 30% and 35% to 50% (mild and severe flow-limiting stenosis, FLS). MCE was performed with low-energy imaging during Optison infusion. After high-energy bubble destruction, time-intensity data from risk beds were fitted for an exponential function as y=A(1-e(-)(bt)), from which the rate of intensity increase (b) and maximal plateau intensity (A) were derived. Although severe NFLS and greater stenoses decreased b with both dobutamine and adenosine, with mild NFLS it was reduced in 58% of animals with dobutamine versus 8% with adenosine. The absolute decrease in b, however, was greater for adenosine than dobutamine with FLS. The A parameter was decreased with both adenosine and dobutamine only with the most severe FLS. Wall thickening was decreased with dobutamine in 33% of animals with severe NFLS and in all animals with any FLS; with adenosine, in all with severe FLS.

CONCLUSIONS

Both dobutamine and adenosine significantly reduce MCE refilling rates in the setting of severe stenosis and in the absence of contractile abnormalities. Dobutamine decreases refilling rate and wall thickening at a less reduced flow grade than adenosine, but adenosine produces a greater magnitude of change than dobutamine.

Assessment of myocardial postreperfusion viability by intravenous myocardial contrast echocardiography: analysis of the intensity and texture of opacification

BACKGROUND

Although defects on intracoronary myocardial contrast echocardiography (MCE) indicate loss of viability after reperfusion, opacified segments may also exhibit persistent dyssynergy. Therefore, we related the intensity and texture of opacification produced by an intravenous contrast agent to histological findings to determine the characteristics of necrotic tissue by postreperfusion MCE.

METHODS AND RESULTS

MCE was performed by intravenous injection of 0.15 mL/kg QW7437 in 14 dogs who underwent 3-hour coronary occlusion followed by 3-hour reperfusion. At baseline and 3 hours after reperfusion, midventricular short-axis images were digitized and segmented. Infarction fraction (IF) for each segment was determined by triphenyltetrazolium chloride stain. Of 224 segments, 140 showed no or small infarction and served as a control group. Of 84 segments with significant infarction (IF>30%), 52 exhibited a defect on MCE, and 32 exhibited no defect. Echo texture was quantified by computing entropy based on the co-occurrence matrix analysis of gray-level pairs within each segment. Three hours after reperfusion, average and maximal entropies in the infarct segments without opacification defects were significantly higher than control levels. Histologically, the degree of intracapillary erythrocyte stasis was less in this group than in the infarcted segments with MCE defects with similar magnitude of tissue injuries.

CONCLUSIONS

Opacification defects by MCE may be present or absent in myocardium with histologically confirmed infarction. The texture of MCE from opacified but infarcted myocardium differed significantly from control segments and may assist in determination of segmental viability after reperfusion.

Effects of aging on left atrial reservoir, conduit, and booster pump function: a multi-institution acoustic quantification study

OBJECTIVE

To assess the feasibility of measuring left atrial (LA) function with acoustic quantification (AQ) and then assess the effects of age and sex on LA reservoir, conduit, and booster pump function.

PATIENTS AND SETTING

165 subjects without cardiovascular disease, 3-79 years old, were enrolled by six tertiary hospital centres.

INTERVENTIONS

Continuous LA AQ area data were acquired and signal averaged to form composite waveforms which were analysed off-line.

MAIN OUTCOME MEASURES

Parameters of LA performance according to age and sex.

RESULTS

Signal averaged LA waveforms were sufficiently stable and detailed to allow automated analysis in all cases. An age related increase in LA area was noted. LA reservoir function did not vary with age or sex. All parameters of LA passive and active emptying revealed a significant age dependency. Overall, the passive emptying phase accounted for 66% of total LA emptying ranging from 76% in the youngest to 44% in the oldest decade. LA contraction accounted for 34% of atrial emptying in all subjects combined with the older subjects being more dependent on atrial booster pump function. When adjusted for atrial size, there were no sex related differences in LA function.

CONCLUSIONS

LA reservoir, conduit, and booster pump function can be assessed with automated analysis of signal averaged LA area waveforms. As LA performance varies with age, establishment of normal values should enhance the evaluation of pathologic states in which LA function is important.

Characterization of contraction and perfusion in the lateral border zone between normal and ischemic myocardium following coronary occlusion by myocardial contrast echocardiography

We performed myocardial contrast echocardography with power Doppler imaging during left anterior descending occlusion in 10 dogs, and found that video intensity and dyssynergy in lateral border zones of ischemic myocardium were present, but the video intensity was significantly lower than adjacent nonischemic zones. The results of this study demonstrate that levels of perfusion and contraction, which are intermediate between normal and central ischemic zones, are observed in the border zone with coronary occlusion by myocardial contrast echocardography, and may have implications in identifying myocardium that will be spared necrosis and in measuring ultimate infarct size.

Quantitative assessment of myocardial perfusion during graded coronary artery stenoses by intravenous myocardial contrast echocardiography

OBJECTIVES

The purpose of this study was to examine whether coronary stenoses of variable severity could be quantitatively assessed by analysis of myocardial perfusion as determined by intravenous (IV) myocardial contrast echocardiography.

BACKGROUND

Recently, new contrast agents and imaging technology have been developed that may enable improved assessment of myocardial perfusion by IV contrast injection.

METHODS

Variable obstruction of the left anterior descending (LAD) coronary artery in dogs was produced by a screw occluder. Coronary artery flow was measured with a transit time flowmeter during baseline, pharmacological vasodilation, a non-flow-limiting stenosis at rest in conjunction with vasodilation, a flow-limiting stenosis, and total occlusion. Myocardial contrast echocardiography was performed after IV injection of the contrast agent NC 100100. Time-intensity curves were obtained off-line for the LAD risk area and the adjacent left circumflex (LCx) territory, and peak background-subtracted video intensity was determined. Fluorescent microspheres were injected at each intervention for determination of regional myocardial blood flow.

RESULTS

During non-flow-limiting stenosis, flow limiting stenosis and total occlusion, LAD/LCx ratios of peak myocardial videointensity and blood flow decreased proportionately. Both LAD/LCx ratios of video intensity and blood flow identified the non-flow-limiting and the flow-limiting stenoses as well as total occlusion of the LAD artery. A significant correlation between LAD/LCx video intensity and blood flow ratios was observed (r = 0.83, p < 0.0001).

CONCLUSIONS

The degree of blood flow mismatch between ischemic and normal myocardial regions during graded coronary stenoses can be estimated in the dog by quantitative assessment of myocardial perfusion produced by IV myocardial contrast echocardiography.

Dilation of the coronary sinus on echocardiogram: prevalence and significance in patients with chronic pulmonary hypertension

BACKGROUND

Although rarely seen in healthy patients, the coronary sinus (CS) is often visualized on echocardiography in patients with right-sided heart disease. However, the prevalence of this finding and its relation to right-sided heart structure and pressure remains undefined.

METHODS

We examined the transthoracic echocardiograms of 43 consecutive patients referred for the evaluation of pulmonary hypertension (26 men, 17 women) with a mean age of 53 +/- 15 years (range 21 to 82 years). Structural abnormalities of the tricuspid valve were absent. All patients underwent right heart catheterization within 48 hours of their echocardiogram, which revealed the following pressures: mean pulmonary artery (50 mm Hg, range 31 to 84 mm Hg) and right atrial (RA) (mean 10, range 1 to 24 mm Hg). Echocardiograms were analyzed for CS size (identified as the smallest diameter of a circular structure in the left atrioventricular groove in the parasternal long-axis view), as well as RA and right ventricular (RV) sizes. The presence and severity (grades 1 through 3) of tricuspid regurgitation (TR) were also recorded.

RESULTS

The CS was visualized in 35 (81%) of 43 patients, and measurements ranged from 0.4 to 1.6 cm (mean 0.8 cm). No difference in RA size, RV size, TR grade, RA pressure (RAP), RV pressure (RVP), mean pulmonary artery pressure (PAP), or pulmonary vascular resistance (PVR) was observed between patients with a visualized and nonvisualized CS. Coronary sinus size correlated significantly with RA size (r = 0.60, P <.001) and pressure (r = 0.59, P <.001), but not with RV size, degree of TR, RVP, PAP, or PVR. Nineteen of 35 patients with a visualized CS underwent pulmonary artery thromboendarterectomy (PTE), and their CS size and RAP were unchanged (0.8 cm and 12 mm Hg, respectively, preand post-PTE; both P = NS [not significant]), though a decrease was observed in other measurements: RA size (4.2 versus 4.8 cm, P =.02), RV size (4.2 versus 5.1 cm, P =.0004), mean PAP (37 versus 72 mm Hg, P <.0001), and PVR (230 versus 899 mm Hg, P <.0001).

CONCLUSIONS

Coronary sinus dilation was observed in 81% of a selected group of patients with pulmonary hypertension in the absence of structural disease of the tricuspid valve. Coronary sinus dilation is related to RAP and RA size, but not to RV size, degree of TR, RVP, PA pressure, or PVR. Once dilated, CS size does not change shortly after decreases of RA size, RV size, or PA pressure produced by PTE.

Quantitative assessment of myocardial perfusion during graded coronary stenosis by real-time myocardial contrast echo refilling curves

OBJECTIVES

The present study examined the ability of real-time myocardial contrast echocardiography (MCE) to delineate abnormalities produced by graded coronary stenoses and to correlate signal intensity (SI) parameters derived from destruction/refilling curves with regional myocardial blood flow (MBF) and contractile function.

BACKGROUND

Recent technological advances have enabled myocardial opacification by MCE to be achieved during real-time imaging.

METHODS

In eight open-chest dogs, we created LAD occlusion and graded stenoses that were either flow-limiting at rest (FLS) or reduced adenosine hyperemia (non-flow-limiting at rest = NFLS). Myocardial contrast echo used Optison infusion and low-energy real-time power pulse inversion imaging. High-energy FLASH frames destroyed bubbles every 15 cardiac cycles. Myocardial SI-versus-time plots were fitted to a one-exponential function to obtain the rate of SI rise (b) and peak SI in the last frame.

RESULTS

Dyssynergy was not observed during any NFLS, but perfusion abnormalities were. Visual detection of decreased opacification was possible with severe NFLS and FLS. b demonstrated a significant reduction with severe NFLS and near significant with moderate NFLS; peak SI did not. All exponential parameters were significantly decreased with FL stenosis and occlusion. The MBF ratio in LAD/LCx beds (fluorescent microspheres) correlated with b (r = 0.79) and the product of the peak SI and b (r = 0.80).

CONCLUSIONS

In an open-chest dog model, parameters derived from microbubble refilling of the imaging field by real-time MCE correlate well with myocardial blood flow and can identify coronary stenosis.

Ischemia-reperfusion injury at the microvascular level: treatment by endothelin A-selective antagonist and evaluation by myocardial contrast echocardiography

BACKGROUND

The purpose of this study was to verify whether endothelin A-antagonist administration at the time of coronary reperfusion preserves postischemic microvasculature and whether myocardial contrast echo (MCE) is able to detect pharmacologically induced changes in microvascular reflow.

METHODS AND RESULTS

Twenty dogs underwent 90 minutes of LAD occlusion (OCC) followed by 180 minutes of reperfusion (RP). Five minutes before LAD reopening, an intravenous bolus (5 mg/kg) of LU 135252 was given in 10 dogs and vehicle in the remaining 10. At baseline (BSL), OCC, and 90 and 180 minutes of RP, microvascular flow (BF) was assessed by microspheres, and MCE was performed with intravenous echo contrast. MCE videointensity and BF were expressed as risk area/control ratio. Myocardial thickness of the risk area was calculated by 2D echo. No differences in BF between the 2 groups were observed at BSL, OCC, and 90 minutes of RP. At 180 minutes of RP, BF was decreased in controls (70+/-7.4% of BSL; P:<0.005 versus BSL) and preserved in LU 135252-treated animals (89+/-4% of BSL; P=NS versus BSL; P<0.05 versus controls). Videointensity at MCE closely followed the changes in BF observed in both groups throughout the protocol. Myocardial thickness at 180 minutes of RP increased to 138.6+/-9.9% of BSL in controls and remained at 108.9+/-7.4% of BSL in treated dogs (P<0.05).

CONCLUSIONS

Endothelin A-antagonist treatment at the time of reperfusion significantly limited the progressive decrease in postischemic microvascular reflow and the increase in myocardial thickness. MCE allowed a reliable evaluation of pharmacologically induced changes in microvascular flow.

Assessment of coronary stenosis severity and transmural perfusion gradient by myocardial contrast echocardiography: comparison of gray-scale B-mode with power Doppler imaging

BACKGROUND

The present study (1) compared the ability of power Doppler imaging with that of gray-scale B-mode tissue imaging to opacify the myocardium and detect coronary stenosis by myocardial contrast echocardiography and (2) compared the response of video intensity (VI) to variable pulsing intervals for each modality.

METHODS AND RESULTS

Four grades of left anterior descending coronary artery (LAD) stenoses were created in 9 open-chest dogs. Stenoses reduced resting LAD flow by 25%, 50%, 75%, and 100% of baseline by flow probe. Myocardial contrast echocardiography was performed during varying ECG gated pulsing intervals (PIs) from 1:1 to 1:10. By gray-scale imaging, background-subtracted LAD bed VI was less than baseline VI at all PIs for the 100% reduced-flow state but not for any other flow state or interval. By power Doppler imaging, LAD bed VI was less than baseline VI at all intervals for 75% and 100% reduced-flow states but only 1:1 and 1:2 for 25% and 50% reduced-flow states, respectively. Correlation of VI and myocardial blood flow (determined by use of fluorescent microspheres) ratios from stenosed versus normal beds was stronger by power Doppler imaging. A transmural opacification gradient with stenosis was visualized and measured by power Doppler imaging, but it was insignificant by gray-scale imaging. The ratio of endocardial/epicardial flow determined by use of fluorescent microspheres was correlated with VI by power Doppler imaging at all PIs.

CONCLUSIONS

Power Doppler imaging has advantages compared with gray-scale imaging in opacifying the myocardium and in detecting coronary stenosis and altered transmural distribution of myocardial perfusion from peak VI. Because VI differences from baseline at long PI vary for mild versus severe (75% and 100%, respectively) reduced-flow states, power Doppler imaging may provide a method to quantify coronary stenoses.

Contrast echocardiography: current and future applications

Recent updates in the field of echocardiography have resulted in improvements in image quality, especially in those patients whose ultrasonographic (ultrasound) evaluation was previously suboptimal. Intravenous contrast agents are now available in the United States and Europe for the indication of left ventricular opacification and enhanced endocardial border delineation. The use of contrast enables acquisition of ultrasound images of improved quality. The technique is especially useful in obese patients and those with lung disease. Patients in these categories comprise approximately 10% to 20% of routine echocardiographic examinations. Stress echocardiography examinations can be even more challenging, as the image acquisition time factor is critically important for accurate detection of coronary disease. Improvements in image quality with intravenous contrast agents can facilitate image acquisition and enhance delineation of regional wall motion abnormalities at the peak level of exercise. Recent phase III clinical trial data on the use of Optison and several other agents (currently under evaluation) have revealed that for approximately half of patients, image quality substantively improves, which enables the examination to be salvaged and/or increases diagnostic accuracy. For the "difficult-to-image" patient, this added information results in (1) enhanced laboratory efficiency, (2) a reduction in downstream testing, and (3) possible improvements in patient outcome. In addition, substantial research efforts are underway to use ultrasound contrast agents for assessment of myocardial perfusion. The detection of myocardial perfusion during echocardiographic examinations will permit the simultaneous assessment of global and regional myocardial structure, function, and perfusion-all of the indicators necessary to enable the optimal noninvasive assessment of coronary artery disease. Despite the added benefit in improved efficacy of testing, few data exist regarding the long-term effectiveness of these agents. Currently under evaluation are the clinical and economic outcome implications of intravenous contrast agent use for daily clinical decision making in a variety of patient subsets. Until these data are known, this document offers a preliminary synthesis of available evidence on the value of intravenous contrast agents for use in rest and stress echocardiography. At present, it is the position of this guideline committee that intravenous contrast agents demonstrate substantial value in the difficult-to-image patient with comorbid conditions limiting an ultrasound evaluation of the heart. For such patients, the use of intravenous contrast agents should be encouraged as a means to provide added diagnostic information and to streamline early detection and treatment of underlying cardiac pathophysiology. As with all new technology, this document will require updates and revisions as additional data become available.

Microvascular damage during myocardial ischemia-reperfusion: pathophysiology, clinical implications and potential therapeutic approach evaluated by myocardial contrast echocardiography

During myocardial ischemia produced by coronary occlusion, coronary microvessels and cardiac myocytes undergo progressive functional and structural changes. The prompt reopening of the epicardial vessel is the main therapeutic strategy to limit the vascular and cellular damage. However, the full benefit of reperfusion can be limited by progressive microvascular obstruction and cell death occurring after the reestablishment of flow. During ischemia-reperfusion, preservation of the integrity of the coronary microvasculature is a fundamental prerequisite to ensuring myocardial viability. Therefore, therapeutic approaches should be developed to prevent and treat microvascular impairment resulting from ischemia-reperfusion. Also, given the importance of the assessment and treatment of post-reperfusion disorders of coronary microvasculature, a diagnostic tool able to evaluate the structural and functional status of the microcirculation in vivo is needed. Myocardial contrast echocardiography has been demonstrated to be extremely useful in this setting. In this review, the anatomic and functional characteristics of the coronary microcirculation are described during normal conditions, as well as in the presence of ischemia-reperfusion injury. The role of myocardial contrast echocardiography in the assessment of microvascular dysfunction and specific potential therapeutic approaches to the treatment of microvascular damage during ischemia and after reperfusion are also discussed.

Axial movement of the intravascular ultrasound probe during the cardiac cycle: implications for three-dimensional reconstruction and measurements of coronary dimensions

BACKGROUND

Motion of the intravascular ultrasound (IVUS) probe within the coronary artery from cardiac contraction may result in artifacts during 3-dimensional ultrasound image reconstruction and inaccurate measurements of coronary compliance. The purpose of this study was to establish whether longitudinal movement of the IVUS transducer in the coronary artery occurs and to quantify such motion.

METHODS

In 31 patients we positioned IVUS transducers at 59 coronary branch points: 41 in the left anterior descending coronary artery, 11 in the left circumflex coronary artery, and 7 in the right coronary artery. In each image sequence the branching vessel oscillated in and out of the imaging plane during the cardiac cycle, confirming longitudinal transducer movement. The extent of movement was estimated by IVUS from the dimension of the branch vessel traversed. In addition, angiographic visualization and measurement of IVUS probe motion was performed at 17 branch points in 12 patients.

RESULTS

Average longitudinal transducer movement as measured by IVUS was 1.50 +/- 0.80 mm (n = 46, range 0.5 to 5.5 mm). Because IVUS could not account for probe motion that exceeded the vessel branch diameter, the values obtained represent minimum movement. Average probe motion as assessed by cineangiography in a subset of 12 patients was 2.43 +/- 1.42 mm (range 0.57 to 6.56 mm).

CONCLUSIONS

This study establishes that longitudinal movement of IVUS transducers within coronary vessels occurs during the cardiac cycle. Because documented extent of motion may be sufficient to influence analysis, IVUS images are best obtained with electrocardiographic gating.

Feasibility of right ventricular myocardial opacification by contrast echocardiography and comparison with left ventricular intensity

To demonstrate the feasibility and quantify the intensity of right ventricular (RV) myocardial opacification by myocardial contrast echocardiography (MCE), we analyzed MCE produced by intravenous injection of 0.15 ml/kg of QW7437 in 8 closed-chest dogs. MCE could produce visual opacification of the RV wall similar in time course to that of the left ventricular wall, and the data supported the potential role of MCE in evaluating RV hypertrophy, contraction, and perfusion abnormalities.

Flow dynamics of QW7437, a new dodecafluoropentane ultrasound contrast agent, in the microcirculation: microvascular mechanisms for persistent tissue echo enhancement

OBJECTIVES

The purpose of this study was to test the hypothesis that a subgroup of QW7437 microbubbles, dodecafluoropentane-based ultrasound contrast microspheres, resides for prolonged periods in the microvasculature.

BACKGROUND

QW7437 produces echo enhancement in myocardium which may persist relatively longer than opacification in the left ventricular cavity. The mechanism for this persistent enhancement remains unknown.

METHODS

The transit of fluorescently labeled erythrocytes was examined by fluorescence intravital microscopy in the microvessels in five rat mesenteries. Ten rats were used to observe the behavior of fluorescently labeled QW7437 microbubbles in the mesenteric microcirculation.

RESULTS

There was no significant change in erythrocyte velocity in the arterioles and venules after the administration of QW7437 microbubbles (0.05 ml/kg) preactivated by negative hydrodynamic pressure. Of 552 microbubbles observed in four arterioles and five capillaries, 549 (99.5%) passed without stoppage (> or = 0.1 s stoppage); only one stopped transiently in arteriole and two in capillaries, each for <0.5 s. Sixty-five of 478 microbubbles (13.6%) observed in six postcapillary venules 11 to 30 microm in diameter and 24 of 408 microbubbles (5.9%) in four venules 31 to 50 microm in diameter stopped transiently (0.1 to 180 s) with an attachment to venular endothelium; the remaining microbubbles passed through the venules without stoppage.

CONCLUSIONS

Prolonged survival as microbubbles in the circulation and transient stoppage of a subgroup of microbubbles in the microvasculature, particularly in venules, are potential mechanisms for the persistent tissue echo enhancement by QW7437 microbubbles during contrast echocardiography.

Infrahepatic interruption of the inferior vena cava with azygos continuation: a potential mimicker of aortic pathology

Infrahepatic interruption of the inferior vena cava (IVC) with azygos or hemiazygos continuation is a rare finding. In this anatomic entity, the intrahepatic segment of the IVC is absent, and the hepatic veins empty directly into the right atrium. Venous blood flow from the lower body is directed from the IVC into the azygos system at the level of the renal veins, with resultant dilation of the azygos and/or hemiazygos veins. Because these enlarged vessels lie parallel to the descending thoracic aorta, they may be mistaken for aortic pathology (dissection, aneurysm, or rupture) during transesophageal echocardiography (TEE). We describe a case of azygos continuation of the IVC initially misdiagnosed by TEE as partial aortic rupture. Repeat TEE with intravenous agitated saline injection correctly identified the condition, and the echocardiographic features are described.

Evaluation of dynamic changes in microvascular flow during ischemia-reperfusion by myocardial contrast echocardiography

BACKGROUND

Dynamic changes of myocardial blood flow have been observed after reperfusion of an occluded coronary artery. MCE performed by intracoronary contrast injection can provide an estimate of microvascular flow. We hypothesized that MCE performed using intravenous infusion of a new generation contrast agent and electrocardiogram-gated harmonic imaging would be able to assess serial changes of microvascular perfusion.

OBJECTIVE

To study the potential of myocardial contrast echocardiography (MCE) to assess serial changes of microvascular flow during ischemia-reperfusion.

METHODS

Sixteen dogs underwent 90 or 180 min of left anterior descending coronary occlusion, followed by 180 min of reperfusion. Regional blood flow (RBF) was measured with fluorescent microspheres at baseline, during coronary occlusion, and at 5, 30, 90, and 180 min during reperfusion. At the same time points, MCE was performed with intravenous infusion of AF0150 (4 mg/min). Gated end-systolic images in short axis were acquired in harmonic mode and digitized on-line. Background-subtracted videointensity measured from MCE and RBF obtained from fluorescent microspheres were calculated for the risk area and for a control area, and were expressed as the ratio of the two areas.

RESULTS

After initial hyperemia, a progressive reduction in flow was observed during reperfusion. MCE correctly detected the time course of changes in flow during occlusion-reperfusion. Videointensity ratio significantly correlated with RBF data (r=0.79; p < 0.0001).

CONCLUSIONS

The progressive reduction in blood flow occurring within the postischemic microcirculation was accurately detected by MCE. This approach has potential application in the evaluation and management of postischemic reperfusion in humans.

Phase III multicenter trial comparing the efficacy of 2% dodecafluoropentane emulsion (EchoGen) and sonicated 5% human albumin (Albunex) as ultrasound contrast agents in patients with suboptimal echocardiograms

OBJECTIVES

This study was performed to compare the safety and efficacy of intravenous 2% dodecafluoropentane (DDFP) emulsion (EchoGen) with that of active control (sonicated human albumin [Albunex]) for left ventricular (LV) cavity opacification in adult patients with a suboptimal echocardiogram.

BACKGROUND

The development of new fluorocarbon-based echocardiographic contrast agents such as DDFP has allowed opacification of the left ventricle after peripheral venous injection. We hypothesized that DDFP was clinically superior to the Food and Drug Administration-approved active control.

METHODS

This was a Phase III, multicenter, single-blind, active controlled trial. Sequential intravenous injections of active control and DDFP were given 30 min apart to 254 patients with a suboptimal echocardiogram, defined as one in which the endocardial borders were not visible in at least two segments in either the apical two- or four-chamber views. Studies were interpreted in blinded manner by two readers and the investigators.

RESULTS

Full or intermediate LV cavity opacification was more frequently observed after DDFP than after active control (78% vs. 31% for reader A; 69% vs. 34% for reader B; 83% vs. 55% for the investigators, p < 0.0001). LV cavity opacification scores were higher with DDFP (2.0 to 2.5 vs. 1.1 to 1.5, p < 0.0001). Endocardial border delineation was improved by DDFP in 88% of patients versus 45% with active control (p < 0.001). Similar improvement was seen for duration of contrast effect, salvage of suboptimal echocardiograms, diagnostic confidence and potential to affect patient management. There was no difference between agents in the number of patients with adverse events attributed to the test agent (9% for DDFP vs. 6% for active control, p = 0.92).

CONCLUSIONS

This Phase III multicenter trial demonstrates that DDFP is superior to sonicated human albumin for LV cavity opacification, endocardial border definition, duration of effect, salvage of suboptimal echocardiograms, diagnostic confidence and potential to influence patient management. The two agents had similar safety profiles.

Feasibility of "limited" echo imaging: characterization of incidental findings

To evaluate the feasibility of limiting the extent of the echocardiographic examination without omitting significant incidental findings, we reviewed consecutive reports from full echo studies performed in a tertiary medical center with the following referral questions: "rule-out pericardial effusion" (n = 40) and "rule-out source of embolus" (n = 132). Specific limited echo imaging protocols were formulated without unnecessary imaging (that is, unrelated to the diagnostic question) or use of Doppler. The percentage of full echo studies with significant incidental findings was determined, categorized by patient age, and then recalculated by whether the specific limited imaging protocol could potentially detect any or all of the incidental findings. The percentage of cases with significant incidental findings was 45% and 36% in the "rule-out" pericardial effusion and source of embolus groups, respectively. This percentage was dependent on age <65 years versus > or =65 years (22% vs 42%, p < 0.005). Limited imaging protocols could identify > or =85% of cases with significant incidental findings. These data suggest that limited echo imaging may be feasible in certain patient groups and referral diagnoses.

Real-time three-dimensional echocardiography for determining right ventricular stroke volume in an animal model of chronic right ventricular volume overload

BACKGROUND

The lack of a suitable noninvasive method for assessing right ventricular (RV) volume and function has been a major deficiency of two-dimensional (2D) echocardiography. The aim of our animal study was to test a new real-time three-dimensional (3D) echo imaging system for evaluating RV stroke volumes.

METHODS AND RESULTS

Three to 6 months before hemodynamic and 3D ultrasonic study, the pulmonary valve was excised from 6 sheep (31 to 59 kg) to induce RV volume overload. At the subsequent session, a total of 14 different steady-state hemodynamic conditions were studied. Electromagnetic (EM) flow probes were used for obtaining aortic and pulmonic flows. A unique phased-array volumetric 3D imaging system developed at the Duke University Center for Emerging Cardiovascular Technology was used for ultrasonic imaging. Real-time volumetric images of the RV were digitally stored, and RV stroke volumes were determined by use of parallel slices of the 3D RV data set and subtraction of end-systolic cavity volumes from end-diastolic cavity volumes. Multiple regression analyses showed a good correlation and agreement between the EM-obtained RV stroke volumes (range, 16 to 42 mL/beat) and those obtained by the new real-time 3D method (r=0.80; mean difference, -2.7+/-6.4 mL/beat).

CONCLUSIONS

The real-time 3D system provided good estimation of strictly quantified reference RV stroke volumes, suggesting an important application of this new 3D method.

Contraction and relaxation velocities of the normal left ventricle using pulsed-wave tissue Doppler echocardiography

We designed the present study (1) to investigate the velocities of longitudinal movement of the human left ventricle by pulsed-wave tissue Doppler (PWTD) imaging; (2) to test the hypothesis that a heterogeneous pattern of longitudinal systolic and diastolic velocities exists among individual left ventricular wall segments; (3) to establish the range of this heterogeneity, and (4) to correlate the function of individual segments with the known orientation of myocardial fibers. PWTD is a novel ultrasound method to quantify myocardial contraction and relaxation velocities. In 27 young normal subjects, PWTD peak values of longitudinal systolic and diastolic velocities were measured for 12 left ventricular segments visualized from the apical window. The PWTD sampling of each myocardial segment resulted in a triphasic velocity curve during each cardiac cycle: a systolic velocity wave (S) directed toward the transducer, and an early diastolic (E) and a late diastolic (A) velocity wave away from the transducer. A heterogeneous pattern of systolic and diastolic myocardial velocities was observed between individual wall segments as well as for the basal and midsegments of each myocardial wall. The difference between the highest and lowest values for S was 38.4% in the basal segments and 56.3% in the midwall segments. The difference between low and high velocities for E was 61.4% in the basal and 38.2% in the midsegments; for A the difference was 29.5% in the basal and 32.6% in the midsegments. In general, lower velocity values were found in the septum with higher basal to midwall difference. The lateral and posterior walls had higher, but more uniform, velocities. PWTD enables the quantitative assessment of regional systolic and diastolic myocardial velocities. Substantial heterogeneity of velocities exists within individual myocardial segments, and must be taken into account in any clinical application. The observed heterogeneity in longitudinal function is consistent with the known spatial distribution of myocardial fibers.

Detection of perfusion defects during coronary occlusion and myocardial reperfusion after thrombolysis by intravenous administration of the echo-enhancing agent BR1

The purpose of this study was to detect myocardial perfusion defects as a result of coronary occlusion and myocardial reperfusion after thrombolysis with intravenous (i.v.) administration of the echo contrast agent BR1 (Bracco Research, Switzerland), which consists of microbubbles (median diameter 2.5 microm) containing sulfur exafluoride in a phospholipidic shell. To generate a coronary thrombosis, a copper coil was advanced into the left circumflex coronary artery in eight anesthetized dogs with opened chest cavities. Coronary occlusion occurred 18 +/- 10 minutes after the insertion of the coil and was documented both by an electromagnetic flow meter (as zero blood flow) and by radiolabeled microspheres (as myocardial perfusion defect). After 2 hours of occlusion, streptokinase was infused i.v.; reperfusion was documented by both the flow-meter and microspheres. Left ventricular cavity enhancement was apparent after all contrast injections. Peak cavity intensity did not increase with dose and was not affected by signal processing (suggesting signal saturation), whereas the duration of contrast effect significantly increased with the dose (from 26 +/- 16 to 147 +/- 74 seconds). Myocardial contrast intensity also increased after contrast (from 15 +/- 12 to 21 +/- 18 gray level/pixel, p < 0.001). Contrast echo detected myocardial perfusion defects (corresponding to 17% +/- 11% of LV cross-sectional area) in all the injections performed during coronary occlusion and detected myocardial reperfusion with a sensitivity of 50% versus microspheres. The extent of perfusion defects by contrast echo showed a good correlation with microspheres (r = 0.73). Myocardial reperfusion was not detected by changes in heart rate, aortic pressure, pulmonary arterial pressure, cardiac output, left ventricular fractional area change, or wall-motion score index. Hemodynamic parameters were not affected by contrast injections. Thus, the i.v. administration of BR1 allows us to accurately detect myocardial perfusion defects during coronary occlusion and, to a lesser extent, myocardial reperfusion after thrombolysis.

Relation of contrast echo intensity and flow velocity to the amplification of contrast opacification produced by intermittent ultrasound transmission

Intermittent ultrasound transmission during contrast echocardiography, so-called transient response imaging (TRI), amplifies contrast intensity. This effect of TRI is attributed to decreased microbubble destruction by reduced exposure time to ultrasound energy. The present study examined the hypothesis that the signal amplification produced by TRI is related to the baseline intensity present in the image and the velocity of flow. We performed second harmonic (2.5/5.0 MHz) imaging during both continuous (frame rate 55 Hz) and electrocardiogram-triggered TRI mode. Contrast images produced by perfluorohexane microbubbles (AF0150) in a steady flow model were obtained every minute throughout the decay phase at transit velocities of 8.1, 6.2, 3.4, 1.9, and 0.7 cm/sec. The decay of videointensity over time could be fitted to a sigmoid curve for both imaging modes with r > 0.99 for individual velocities. The intensity with TRI was greater than that with continuous imaging (CI) at any time and velocity. The mean increase in intensity between modes throughout decay was 8.2 +/- 3.7, 12.8 +/- 4.2, 25.7 +/- 5.8, 49.5 +/- 8.0, and 64.0 +/- 14.4 gray levels for the respective velocity levels studied (p < 0.0001). Although varying with baseline intensity at early and late phases, the TRI amplification plateaued during middecay, and within the intensity range of 16 to 143 gray levels for CI and 67 to 186 gray levels for TRI, it showed no overlap among the different velocity levels. Thus the ability of TRI to enhance contrast opacification is much greater at low flow velocities, which has implications regarding the mechanism of TRI effect and preferential visualization of intramyocardial coronary arteries by this agent. Although this effect was influenced by the baseline intensity, it was relatively constant for each velocity level within an optimal intensity range during middecay, providing the basis for flow velocity measurement by contrast echo.

An enhanced method for measuring cardiac output using Doppler color flow echocardiography

An enhanced method for determining cardiac output using Doppler color flow imaging techniques to measure mitral orifice diameter was developed and validated in an experimental model and in clinical patients. In an in vitro circuit model, color jet width correlated well with actual orifice dimension from 12 to 24 mm (r = 0.99). In the clinical application, mitral valve area was calculated as a X b X pi/4 where a and b represent the width of the color flow stream in the mitral orifice just distal to the annulus in apical long-axis (short-diameter) and 4-chamber (90 degrees rotated, long-diameter) views, respectively. Cardiac output was then computed as the product of mitral valve area and time-velocity integral of transmitral flow from the same site. Cardiac output was also measured by thermodilution and conventional echocardiographic methods using diameters and time-velocity integrals from the left ventricular outflow tract. In 30 patients with nonvalvular heart disease, cardiac output measured by thermodilution ranged from 3.40 to 8.40 L/min. Cardiac output was determined in 28 of 30 patients (93%) by the Doppler color flow imaging technique; it ranged from 3.00 to 8.36 L/min and correlated well with thermodilution: y = 0.90x + 0.63, r = 0.91. Cardiac output was determined in 24 of 30 patients by the conventional left ventricular outflow method (80%). The cardiac output measured by the conventional method correlated less closely with thermodilution (r = 0.84), although there was no statistical difference in correlation coefficiencies between the 2 methods. These results indicate that the Doppler color flow imaging technique can be used to enhance the determination of cardiac output by echocardiography, particularly when the conventional method has resulted in technically inadequate recordings.

The emerging role of contrast agents in echocardiography

Because of an outstanding track record for diagnostic accuracy, noninvasive properties, ease of use, and relatively low expense, echocardiography has become a leading technique in the evaluation of cardiac disorders. In the three decades since echocardiography entered the ranks of standard cardiac diagnostic tools, refinements and technological advances have progressively increased its usefulness. One of the most noteworthy advancements has been the development of ultrasound contrast agents, which investigators are avidly seeking to apply to a broad spectrum of clinical settings and issues.

Development and validation of a noninvasive method to determine arterial pressure and vascular compliance

The ability not only to record automated systolic and diastolic pressure, but also to derive measurements of the rate of pressure change during the cardiac cycle, would have great potential clinical value. A new method has been developed to obtain pressure measurements at 20-ms intervals by oscillometric cuff signal pattern recognition. Derivation of noninvasive pressure measurements is based on a T tube aorta and straight tube brachial artery, and assumes that the systolic phase of the suprasystolic cuff signal and the diastolic phase of the subdiastolic cuff signal most closely approximate systolic and diastolic aortic pressures, respectively. Arterial pressures obtained by this method were compared with simultaneous invasive measurements from the thoracic aorta in 36 patients. Good agreement was observed between noninvasive and invasive methods for systolic (146 +/- 4 vs 145 +/- 5 mm Hg), diastolic (80 +/- 2 vs 77 +/- 2 mm Hg), and mean (100 +/- 3 vs 100 +/- 3 mm Hg) arterial pressures, and correlation coefficients were r = 0.94, 0.91, and 0.95, respectively. To assess the validity of measurements of the rate of pressure change, oscillometric cuff signals from a subgroup of 14 patients were analyzed in detail for the peak positive pressure derivative (dP/dt(Max)), peak negative pressure derivative (dP/dt(Min)), and time interval between peak positive and peak negative pressure derivatives [t(pp)]. Results (mean +/- SEM) were: [table in text]. The incorporation of measurements of the rate of pressure change into a physical model of the brachial artery was used to derive vascular compliance. A significant correlation was observed between vascular compliance derived from the oscillometric signal and determinations by either thermodilution or Fick methods and noninvasive pressures (n = 20, r = 0.83, p <0.001). Day-to-day variability for blood pressure and vascular compliance derived by the noninvasive method did not differ by >4%, representing a reproducible measure of vascular structure and function. We conclude that the measurement of absolute pressure and rate of pressure change show good correlation with catheter data and that vascular compliance can be reliably assessed by this new method. The technology should provide a valuable noninvasive tool for the assessment of both cardiac function and vascular properties.

Effects of short-term administration of sublingual nifedipine on coronary arterial wall elastic properties: evaluation by intravascular ultrasound

Intravascular ultrasound is suited to measure coronary cross-sectional anatomy. Therefore the regional coronary wall elasticity was evaluated by examining the response to nifedipine. In 20 patients, coronary ostial pressure (P) and intravascular ultrasound images were simultaneously recorded before and after sublingual administration of 10 mg nifedipine. We identified the perimeter of the vessel wall, with normal or atherosclerotic plaque, on ultrasound image. At the atherosclerotic site, we measured segmental perimeter (S) for each normal or plaque segment. The ratio of the individual segment length (delta S/delta P) and cyclic variation of cross-sectional area (delta A/delta P) per mm Hg increase in P were calculated. Nifedipine decreased pressure (133/79-120/73 mm Hg) and increased heart rate (79-82 beats/min). After nifedipine, delta A/delta P increased from 8.5 +/- 10.2 x 10(-3) to 16.5 +/- 14.4 x 10(-3) mm2/mm Hg at 20 normal sites (p = 0.005) but was unchanged at 17 atherosclerotic sites (6.6 +/- 7.0 x 10(-3) to 6.7 +/- 7.1 x 10(-3) mm2/mm Hg). Nifedipine increased delta S/delta P in normal segments (4.5 +/- 8.7 x 10(-3) to 9.9 +/- 10.9 x 10(-3) mm/mm Hg; p = 0.02) but produced no change in segments with calcified or soft plaque (-1.1 +/- 0.3 x 10(-3) to 1.4 +/- 1.6 x 10(-3) mm/mm Hg and 5.0 +/- 3.6 x 10(-3) to 6.1 +/- 4.8 x 10(-3) mm/mm Hg, respectively). This study demonstrated that nifedipine increases regional coronary arterial elasticity at normal segments but not at that containing mildly atherosclerotic segment, and likely that the arterial wall function indicated by the response to nifedipine was impaired at an early stage of atherosclerosis.

Requirement for accurate measurement of regurgitant stroke volume by the combined continuous-wave Doppler and color Doppler flow convergence method

The examination conditions necessary for accurate measurement of regurgitant volume by the proximal flow convergence method applying a simple hemispheric equation remain uncertain. This study investigated the requirement for measuring regurgitant stroke volume from the combined continuous-wave and color Doppler proximal flow convergence approach. Twenty-five pulsatile flow rates were produced by driving five regurgitant stroke volumes ranging from 30 to 70 ml/beat through planar orifices with cross-sectional areas ranging from 0.10 to 1.0 cm2. Four different shaped orifices (circular, rectangular with a major/minor axis ratio 2:1, slitlike with a major/minor axis ratio of 8:1, and square) having identical orifice areas (0.5 cm2) were examined. Regurgitant volume (RV) was estimated from the combined continuous-wave and color Doppler approach according to the previously described equation RV = 2 pi x (r max)2 x AV x (TVI/Vmax), where r max is maximal radial distance, AV is aliasing velocity, TVI is time velocity integral of regurgitant jet, and Vmax is peak velocity of regurgitant jet. Plotting the difference between actual and calculated RV versus radial distance of the proximal convergence shell for each flow rate from circular to rectangular orifices yielded curves conforming to a curvilinear function that crossed the point of zero difference at 1.0 cm. However, in the slitilke orifice, a more remote distance (1.6 cm) is required for the best agreement. Actual regurgitant stroke volume can be estimated well by the combined continuous-wave Doppler and proximal flow convergence method applying a simple hemispheric equation if an aliasing velocity is used that results in a radial distance of at least 1.0 cm.

Effect of managed care on cardiovascular specialists: involvement, attitudes and practice adaptations

OBJECTIVES

This study was undertaken to determine the extent to which cardiovascular specialists are involved with and affected by managed care and to ascertain their attitudes toward it. This survey also served as the follow-up to an initial study on the subject performed by the American College of Cardiology in 1993.

BACKGROUND

The initial 1993 study was performed to address the lack of any comprehensive examination of the impact of managed care on cardiovascular specialists. In 1995, to reexplore this question and follow up the 1993 findings, the College conducted a survey of its membership in the following areas: 1) physician relationship with managed care plans; 2) number of managed care contracts; 3) breakdown of revenue by payment source; 4) changes in practice in response to managed care; and 5) physician attitudes toward managed care. To the extent feasible, the 1995 questionnaire paralleled the 1993 instrument to facilitate comparisons.

METHODS

A questionnaire was mailed to 5,147 practicing College members in the United States, who were categorized by specialty as pediatric cardiologists, adult cardiologists or cardiovascular surgeons. Mailings were sent to 1) all pediatric cardiologists and cardiovascular surgeons; 2) randomly selected adult cardiologists practicing in 10 states with high managed care penetration; and 3) randomly selected adult cardiologists in the nine U.S. census areas who were not practicing in the 10 states with high managed care penetration.

RESULTS

Usable surveys were returned by 1,236 respondents, for an overall response rate of 24%. Involvement with at least one type of managed care organization was reported by 89% of respondents, up from 76% in 1993. Although managed care relationships had increased across physician age, region, practice and specialty, respondents indicated that, on average, well below 50% of their practice revenues stem from managed care contracts. To adapt to the managed care environment, strategic practice changes, such as joining a cardiovascular network, implementing continuous quality improvement systems and adopting clinical pathways, were being instituted by most respondent practices of nine or more physicians. Smaller groups were less active. Most respondents involved with managed care disliked its effects, particularly in clinical matters. Their attitudes toward the assumption of risk, managed fee-for-service arrangements and a private versus single-payer system show that there is no uniformity of opinion regarding the best means to contain costs and promote efficiency.

CONCLUSIONS

Managed care has become an established part of cardiovascular specialist practice in the United States. Although this trend is viewed with some disfavor, most respondents are making practice changes to adapt to this new environment.

Arterial compliance by cuff sphygmomanometer. Application to hypertension and early changes in subjects at genetic risk

Abnormalities of the arterial pulse waveform reflect changes in cardiovascular structure and function. These abnormalities may occur early in the course of essential hypertension, even before the onset of blood pressure elevation. Previous studies of cardiovascular structure and function have relied on invasive intra-arterial cannulation to obtain the arterial pulse wave. We evaluated arterial structure and function using a noninvasive cuff sphygmomanometer in hypertensive (n = 15) and normotensive (n = 36) subjects stratified by genetic risk (family history) for hypertension. Using a simple physical model in which the aorta was assumed to be a T tube and the brachial artery a straight tube, we determined vascular compliance and peripheral resistance by analyzing the brachial artery pulsation signal from a cuff sphygmomanometer. Essential hypertensive subjects tended to have higher peripheral resistance (P = .06) and significantly lower vascular compliance (P = .001) than normotensive subjects. Vascular compliance correlated with simultaneously determined pulse pressure in both groups (n = 51, r = .74, P < .0001). Higher peripheral resistance (P = .07) and lower vascular compliance (P = .04) were already found in still-normotensive offspring of hypertensive parents (ie, normotensive subjects with a positive family history of hypertension) than in normotensive subjects with a negative family history of hypertension. Multivariate analysis demonstrated that both genetic risk for hypertension (P = .030) and blood pressure status (P = .041), although not age (P = .207), were significant predictors of vascular compliance (multiple R = .47, P = .011). However, by two-way ANOVA, genetic risk for hypertension was an even more significant determinant (F = 7.84, P = .007) of compliance than blood pressure status (F = 2.69, P = .089). Antihypertensive therapy with angiotensin-converting enzyme inhibitors (10 days, n = 10) improved vascular compliance (P = .02) and reduced resistance (P = .003) significantly; treatment with calcium channel antagonists (4 weeks, n = 8) tended to improve vascular compliance (P = .07) and significantly reduced peripheral resistance (P = .006). We conclude that arterial vascular compliance abnormalities detected by a noninvasive cuff sphygmomanometer reflect treatment-reversible changes in vascular structure and function. Early changes in vascular compliance in still-normotensive individuals at genetic risk for hypertension may be a heritable pathogenetic feature of this disorder.

Distortion of intravascular ultrasound images because of nonuniform angular velocity of mechanical-type transducers

The purpose of this study was to quantify nonuniform rotation in a current mechanical intravascular ultrasound (IVUS) instrument and its effect on arc, area, and diameter measurements. The accurate reconstruction of IVUS two-dimensional images is dependent on uniform rotation of the catheter tip. Prior investigations suggested that bends in the catheter driveshaft may be responsible for poor torque transmission, nonuniform rotation, and consequent errors in IVUS measurements. Eight 30 MHz mechanically driven IVUS catheters were evaluated in a model simulating the catheter course through the aorta and coronary ostium in a clinical study. Angular velocity and posi-ion profiles of the transducer, image angle, and diameter and area measurement errors were obtained from each catheter by imaging a vascular phantom with eight equispaced echogenic markers from concentric and eccentric positions. Six catheters also were tested for comparison in a simple curvature model. Rotational error was found in all catheters tested and worsened in the aortic model. Maximal angular error, defined as the largest angle between actual and presumed transducer direction, increased when measured in the aortic model as compared with the simple curvature model (17 +/- 12 degrees to 45 +/- 25 degrees; p < 0.05). Angles of 45 degrees were misrepresented with a mean range of values of 26 to 63 degrees. With eccentric catheter placement, area and diameters had average maximal absolute errors of 26% +/- 7.8% and 23% +/- 10%, respectively. In conclusion, nonuniform rotation of mechanical IVUS transducers constitutes a significant potential source of error in IVUS measurement of arcs of calcification, and lumen shape, area, and diameter.

Intracoronary gene transfer of fibroblast growth factor-5 increases blood flow and contractile function in an ischemic region of the heart

Increased coronary blood vessel development could potentially benefit patients with ischemic heart disease. In a model of stress-induced myocardial ischemia, intracoronary injection of a recombinant adenovirus expressing human fibroblast growth factor-5 (FGF-5) resulted in messenger RNA and protein expression of the transferred gene. Two weeks after gene transfer, regional abnormalities in stress-induced function and blood flow were improved, effects that persisted for 12 weeks. Improved blood flow and function were associated with evidence of angiogenesis. This report documents, for the first time, successful amelioration of abnormalities in myocardial blood flow and function following in vivo gene transfer.

Relation of Doppler transmitral flow patterns to functional status in congestive heart failure

We analyzed the relation of Doppler transmitral flow patterns and New York Heart Association (NYHA) classification in 60 consecutive patients with heart failure (44 men and 16 women; mean age 58 +/- 13 years) with left ventricular ejection fraction of < 40 percent. Of the study population, 40 patients with mild to moderate heart failure underwent symptom-limited exercise testing. The relation of transmitral flow pattern and exercise tolerance was also analyzed. Doppler echocardiography was performed in all patients. The patients were subdivided into nonrestrictive and restrictive groups according to the pattern. The univariate analysis showed a relation for left ventricular ejection fraction (p = 0.01 by analysis of variance testing) and transmitral flow pattern (p = 0.0003 by chi-squared test) with NYHA classification. When the multivariate regression analysis was performed, only the restrictive pattern by Doppler emerged as an independent determinant of the advanced NYHA class (p = 0.005). In mild to moderate congestive heart failure, patients with nonrestrictive pattern exercised significantly longer than those with the restrictive pattern by an average of 133 seconds (p = 0.003) despite comparable reductions in ejection fraction. Thus the restrictive transmitral flow pattern by Doppler is a noninvasive marker for severe symptoms and diminished exercise tolerance in heart failure patients.

Atheroma morphology and distribution in proximal left anterior descending coronary artery: in vivo observations

OBJECTIVES

This study sought to examine, in vivo, the shape and position of atheroma in the proximal left anterior descending coronary artery.

BACKGROUND

The prevalence, shape and location of atheromas involving the proximal left anterior descending artery have implications regarding the role of disturbed shear forces in the genesis of atherosclerosis. However, no data are available regarding in vivo findings or advanced disease.

METHODS

Forty-two consecutive high quality intravascular ultrasound images were examined from patients with atherosclerotic disease in the proximal left anterior descending artery just distal to the left main bifurcation. Lesion percent area stenosis and maximal, minimal and flow divider intimal-medial thickness were measured at the region immediately after the circumflex takeoff. The angle formed by the midpoint of the flow divider, the human center of gravity and the maximal plaque thickness were determined.

RESULTS

Eccentricity of vessel wall atheroma was observed such that the maximal wall thickness (1.42 +/- 0.50 mm [mean +/- SD]) differed significantly from minimal wall thickness (0.17 +/- 0.098 mm). Further, the region of vessel wall manifesting maximal thickness was greater than the flow divider thickness (0.26 +/- 0.16 mm). Maximal plaque thickness spared the region of the flow divider in 100% of cases and was positioned at a mean angle of 193 +/- 49 degrees from the center of the flow divider. Eccentric morphology was maintained across the 24% to 80% range of area stenosis.

CONCLUSIONS

Atheromas in the very proximal left anterior descending artery are located opposite the circumflex takeoff, spare the flow divider and maintain eccentricity across a wide range of vessel stenoses. These in vivo morphologic data support the potential role of fluid dynamic mechanical factors in atherogenesis and have implications regarding the success of catheter-based interventional procedures at the site.