Deterioration in right ventricular structure and function over time in patients with heart failure and preserved ejection fraction

AIMS

Prevalent right ventricular (RV) dysfunction (RVD) is associated with increased mortality in patients with heart failure with preserved ejection fraction (HFpEF), but no study has characterized long-term changes in RV structure and function within the same patient.

METHODS AND RESULTS

Patients with unequivocal HFpEF defined by either invasive haemodynamics or hospitalization for pulmonary oedema (n = 271) underwent serial echocardiographic evaluations >6 months apart. Clinical, structural, functional, and haemodynamic characteristics were examined. Over a median of 4.0 years (interquartile range 2.1-6.1), there was a 10% decline in RV fractional area change and 21% increase in RV diastolic area (both P < 0.0001). These changes greatly exceeded corresponding changes in the left ventricle. The prevalence of tricuspid regurgitation increased by 45%. Of 238 patients with normal RV function at Exam 1, 55 (23%) developed RVD during follow-up. Development of RVD was associated with both prevalent and incident atrial fibrillation (AF), higher body weight, coronary disease, higher pulmonary artery and left ventricular filling pressures, and RV dilation. Patients with HFpEF developing incident RVD had nearly two-fold increased risk of death (adjusted hazard ratio 1.89, 95% confidence interval 1.01-3.44; P = 0.04).

CONCLUSION

While previous attention has centred on the left ventricle in HFpEF, these data show that right ventricular structure and function deteriorate to greater extent over time when compared with changes in the left ventricle. Further study is required to evaluate whether interventions targeting modifiable risk factors identified for incident RVD, including abnormal haemodynamics, AF, coronary disease, and obesity, can prevent RVD and thus improve outcomes.

Comparison of a Synthetic Antithrombin III-binding Pentasaccharide and Standard Heparin as an Adjunct to Coronary Thrombolysis

The effects on alteplase-induced thrombolysis of the synthetic ATIII-binding pentasaccharide SR90107A/ORG 31540 (synthetic pentasaccharide, SP) and of standard heparin (SH) were compared in a copper coil model of coronary artery thrombosis in 6 groups of 10 dogs. After 1 h of occlusion, all animals received intravenously alteplase and aspirin, and were randomly assigned to a 2 h infusion of either saline, or one of two doses of SH (100 IU/kg bolus plus 50 IU/kg/h infusion, or 200 IU/kg bolus plus 100 IU/kg/h infusion), or one of three doses of SP (100 nmol/kg bolus plus 50 nmol/kg/h infusion, 200 nmol/kg bolus plus 100 nmol/kg/h infusion, or 400 nmol/kg bolus plus 200 nmol/kg/h infusion). Coronary angiography was performed every 10 min for 4 h. Appropriate doses of SP and SH enhanced alteplase-induced thrombolysis to a similar extent. In contrast, SP was devoid of any anti-IIa activity or aPTT prolongation.

Robot-assisted repair of tricuspid leaflet prolapse using standard valvuloplasty techniques

While minimally invasive approaches are used routinely to correct severe mitral regurgitation due to leaflet prolapse, isolated tricuspid valve prolapse is less frequent and usually addressed via sternotomy. A 34-year-old female presented with exertional dyspnea and severe tricuspid regurgitation due to an unsupported anterior leaflet causing prolapse, a tethered septal leaflet, and dilated annulus. Herein, the technique is described of a robot-assisted tricuspid valve repair using established open valvuloplasty principles. The robotic repair was performed by the placement of Gore-Tex neochordae from the anterior papillary muscle to the anterior tricuspid leaflet, plication of the anteroseptal and anteroposterior commissures, closure of an anterior leaflet cleft, and the insertion of an annuloplasty band. The patient had an uncomplicated hospital course and was dismissed home on the third postoperative day.

Endothelial progenitor cells restore renal function in chronic experimental renovascular disease

BACKGROUND

Endothelial progenitor cells (EPCs) promote neovascularization and endothelial repair. Renal artery stenosis (RAS) may impair renal function by inducing intrarenal microvascular injury and remodeling. We investigated whether replenishment with EPCs would protect the renal microcirculation in chronic experimental renovascular disease.

METHODS AND RESULTS

Single-kidney hemodynamics and function were assessed with the use of multidetector computed tomography in vivo in pigs with RAS, pigs with RAS 4 weeks after intrarenal infusion of autologous EPCs, and controls. Renal microvascular remodeling and angiogenic pathways were investigated ex vivo with the use of micro-computed tomography, histology, and Western blotting. EPCs increased renal expression of angiogenic factors, stimulated proliferation and maturation of new vessels, and attenuated renal microvascular remodeling and fibrosis in RAS. Furthermore, EPCs normalized the blunted renal microvascular and filtration function.

CONCLUSIONS

The present study shows that a single intrarenal infusion of autologous EPCs preserved microvascular architecture and function and decreased microvascular remodeling in experimental chronic RAS. It is likely that restoration of the angiogenic cascade by autologous EPCs involved not only generation of new vessels but also acceleration of their maturation and stabilization. This contributed to preserving the blood supply, hemodynamics, and function of the RAS kidney, supporting EPCs as a promising therapeutic intervention for preserving the kidney in renovascular disease.

Intracoronary delivery of Gd-DTPA and Gadophrin-2 for determination of myocardial viability with MR imaging

The aim of this study was to compare intracoronary (i.c.) administration of Gadophrin-2, a necrosis-avid contrast agent (NACA), and nonspecific agent Gd-DTPA for determination of myocardial viability (MV) in acute myocardial infarction (AMI) with MRI. Reperfused AMI was induced in 12 dogs by transcatheter balloon occlusion of coronary artery. In 6 dogs each, Gd-DTPA at 0.1 mmol/kg or Gadophrin-2 at 0.005 mmol/kg was administered into coronary artery by fast bolus (n = 3) or slow infusion (n = 3). Serial ECG-triggered cardiac MRI of T1-weighted segmented turbo fast low-angle shot (FLASH) sequence was conducted and compared with triphenyltetrazolium chloride (TTC) histochemical staining. The contrast ratio and infarct size were quantified and analysed statistically. No cardiovascular side effects were found with local delivery of both agents. After i.c. administration, Gadophrin-2 induced a strong (CR > or = 1.78) and persistent (> or = 10 h) contrast enhancement of infarcted region. The infarct size defined with Gadophrin-2 was almost identical to that with TTC staining throughout the postcontrast period. With a dose 20 times higher, Gd-DTPA also strongly enhanced infarct-to-normal contrast; however, the enhancement diminished with time, i.e. from early strong to later faint enhancement and eventual loss of contrast. The delineated infarct size was also unstable, i.e. from early overestimation to later underestimation and eventual disappearance of the enhanced infarct. In combination with PTCA procedure, i.c. administration of MRI contrast agents may prove useful for post-procedure verification of diagnosis. The NACA-enhanced MRI may serve as an in vivo surrogate of postmortem histochemical staining for determination of MV. Although applicable in clinical setting, cardiac MRI with nonspecific Gd-DTPA is less reliable and should be performed within less than 1 h after contrast.

A nonsurgical porcine model of left ventricular dysfunction. Validation of myocardial viability using dobutamine stress echocardiography and positron emission tomography

BACKGROUND: Although several short-term animal models of stunning and hibernation have been studied extensively, it has been difficult to produce a consistent animal model of chronic hibernation. The aim of the present study was to develop a nonsurgical porcine stent model of coronary stenosis in order to investigate the relationship between chronic dysfunctional myocardium and viability using 2D-echo, dobutamine stress echo (DSE) and positron emission tomography (PET). METHODS AND RESULTS: Focal progressive coronary stenosis was induced by implantation of an oversized stent in the left anterior descending (LAD) and/or circumflex (LCX) coronary artery in a total of 115 pigs, according to various experimental protocols: copper stent in the LAD (group I, n = 5); noncoated stainless steel stent in the LAD combined with balloon overstretch (group II, n = 7); poly(organo)phosphazene-coated stent in the LAD (group III, n = 77); and poly(organo)phosphazene-coated stent in both the LAD and the LCX (group IV, n = 26). Occurrence of left ventricular dysfunction was evaluated weekly by 2D-echo. At the time of left ventricular dysfunction the presence of viable myocardium within the dysfunctional region was investigated with DSE and PET, and confirmed by histology. The degree of coronary artery stenosis was measured by quantitative coronary angiography and morphometry. Severe coronary artery stenosis in the presence of dysfunctional, but viable, myocardium was induced in groups III and IV (47% and 11% of the animals, respectively). CONCLUSIONS: The authors developed a nonsurgical porcine stent model of progressive coronary stenosis using an oversized polymer-coated stent resulting in chronically decreased myocardial function, with residual inotropic reserve and viable myocardium. This condition may arise from repetitive periods of ischemia, or from sustained hypoperfusion, or a combination of these processes eventually leading to myocardial hibernation.

Are changes in myocardial integrated backscatter restricted to the ischemic zone in acute induced ischemia? An in vivo animal study

Integrated backscatter (IB) from a myocardial region, calculated from radiofrequency echocardiographic data, has been proposed as a useful parameter for investigating changes in myocardial tissue induced by ischemia. In 10 closed-chest dogs, 5 minutes of myocardial ischemia was induced by either a proximal occlusion of the circumflex coronary artery (CX) (5 dogs), resulting in extensive ischemia in the posterior wall, or by occluding the distal CX vessel (5 dogs) to produce a small localized ischemic zone in the posterior wall. High-resolution digital radiofrequency data from the whole left ventricular myocardium, in the imaging plane during one complete heart cycle, were acquired with a whole-image real-time acquisition approach. Regions in the septum and posterior wall (both ischemic tissue and, in the case of distal occlusions, tissue surrounding the ischemic zone) were chosen for analysis, and IB and cyclic variation (CV) of IB were calculated. Post occlusion, an increase in mean IB values was found in the ischemic segment. However, an increase in CV was also observed in the peri-ischemic zone for the distal CX occlusion and in the septum after proximal CX occlusion. These findings show that changes in CV are not restricted to the ischemic zone but may also occur in distal myocardium. This may be explained by changes in the regional contractile state and loading conditions of the "normal" myocardium, which are altered in response to the distal ischemia.

High frame rate myocardial integrated backscatter. Does this change our understanding of this acoustic parameter?

AIMS

Integrated backscatter (IB) and its cyclic variation (CV) derived from radio-frequency (RF) data have been used as parameters to attempt myocardial tissue characterization. Prior imaging systems used to measure IB and its CV typically acquired data at frame rates of 20-30 Hz and at a resolution of 6-8 bits. If changes in IB levels are in part related to specific short-lived events, occurring within the cardiac cycle, this frame rate and resolution could have been too low to resolve adequately what might be a more complex data set.

METHODS AND RESULTS

To investigate this possibility, we acquired real time two-dimensional (2D) myocardial IQ data (the 'in-phase quadrature' sampled RF data) at high frame rate (> 100 Hz), high dynamic resolution (theoretical 19-bit) and a sector angle of 20 degrees. Several consecutive heart cycles of myocardial data were acquired from individual cardiac walls in five closed chest dogs and 10 healthy, young volunteers at normal heart rates. On the reconstructed RF data regions of interest were indicated, and IB and its CV were calculated. The extracted high frame rate curves showed that the CV of IB is not a smooth sinusoidal-like curve, but is made up of multiple reproducible peaks and troughs with local minima and maxima which are temporally related to active or passive mechanical events, i.e. systolic contraction, early ventricular relaxation and ventricular filling due to atrial contraction.

CONCLUSIONS

This study shows that increasing the rate of real-time RF data acquisition results in a more complex, reproducible IB curve. The resolved maxima and minima in IB levels are related to specific phases of the myocardial contraction. Furthermore, spectral analysis showed that IB curves acquired at normal heart rates contain information up to 40 Hz. Hence, cardiac imaging data sets used to analyse regional myocardial function obtained at frequencies lower than 80 frames per second can contain aliased information.

Repeated stunning precedes myocardial hibernation in progressive multiple coronary artery obstruction

OBJECTIVE

The aim of this study was to characterize a regional myocardial flow-function relationship in collateral dependent myocardium produced by multiple coronary artery obstruction.

METHODS

Ameroid constrictors were placed around the proximal right (RC) and circumflex (CX) coronary arteries and a silicon tubing cuff around the proximal LAD (left anterior descending artery) (luminal stenosis +/- 77%) in 18 dogs. Weekly two-dimensional echocardiography was performed for regional function (anterior [A], inferoposterior [IP], wall thickening [WT]), and fractional shortening (FS). Colored microspheres injected at baseline and before sacrifice, before and after dipyridamole (0.5 mg/kg) injection, determined resting flow (RF) and coronary reserve (CR), respectively.

RESULTS

Coronary angiography performed at four weeks after surgery confirmed occlusion of RC and CX with collateralization and a tight stenosis of LAD. Initially, an episodic reduction in A and IP WT was observed which became persistent later (AWT: 16 +/- 3%; IPWT: 16 +/- 4%, FS: 20 +/- 4%, p < 0.005 vs. baseline [BS]). With dobutamine a biphasic response (improvement in A and IP WT between 5-15 and dysfunction between 20-30 microg/kg/min) was observed. Seven dogs were sacrificed at eight weeks and showed normal RF but reduced transmural CR (A: 75 +/- 18%; IP: 46 +/- 22% of control). Seven dogs underwent PTCA of the LAD at eight weeks and showed gradual improvement in AWT with normalization at 12 weeks (AWT: 30 +/- 5%, p < 0.001 vs. eight weeks). At sacrifice RF and CR in the A wall were normal but there was reduced subendocardial RF in the IP region (64% of BS). Further, biopsy samples showed normal histological findings and high energy phosphate content in all dogs. Radioligand binding assays using 125I-iodocyanopindolol showed downregulation of beta-adrenergic receptor density in the dysfunctional regions compared with control.

CONCLUSIONS

In this canine model of viable, collateral dependent and reversibly dysfunctional myocardium, there was early episodic dysfunction followed by persistent dysfunction which was initially associated with normal RF and later with subendocardial hypoperfusion.

In vivo effects of contrast media on coronary thrombolysis

OBJECTIVES

The aim of the present study was to evaluate the influence of radiographic contrast media (CM) on alteplase-induced coronary thrombolysis.

BACKGROUND

Contrast media inhibit fibrinolysis in vitro and interact with endothelial cells, platelets and the coagulation system. The in vivo effects of CM on thrombolysis are not known.

METHODS

Occlusive coronary artery thrombosis was induced in 4 groups of 10 dogs by the copper coil technique. After 70 min of occlusion the dogs were randomized to intracoronary injection of 2 ml kg(-1) of either saline, a low-osmolar ionic CM (ioxaglate), a low-osmolar nonionic CM (iohexol) or a high-osmolar ionic CM (amidotrizoate). Thrombolysis with alteplase and co-therapy with aspirin and heparin was initiated after 90 min of occlusion. The coronary artery flow was monitored with an electromagnetic flowmeter throughout the experiment.

RESULTS

Iohexol and amidotrizoate, but not ioxaglate, were associated with longer reperfusion delays (time to optimal reperfusion: 67+/-48 min and 65+/-49 min, respectively, vs. 21+/-11 min after placebo; p < 0.05) and shorter periods of coronary perfusion (optimal perfusion time: 21+/-26 min and 21+/-28 min, respectively, vs. 58+/-40 min after placebo; p < 0.05). No significant differences were observed between groups with regard to activated partial thromboplastin times, circulating thrombin-antithrombin III complex concentrations and fibrinogen.

CONCLUSIONS

In this animal model administration of iohexol and amidotrizoate before thrombolysis significantly delayed reperfusion. This interaction should be considered in the design of clinical trials of thrombolytic therapy that evaluate coronary artery patency and in patients receiving local infusions of fibrinolytic agents.

Local adenovirus-mediated transfer of human endothelial nitric oxide synthase reduces luminal narrowing after coronary angioplasty in pigs

BACKGROUND

Nitric oxide, synthesized from L-arginine by nitric oxide synthase (NOS), is a vasodilator and inhibits vascular smooth muscle cell (SMC) proliferation and migration. The effects of local NOS gene transfer on restenosis after experimental balloon angioplasty were investigated.

METHODS AND RESULTS

Left anterior descending coronary artery angioplasty was performed in 25 pigs. Animals received an intramural injection of adenovirus (1.5 x 10(9) pfu) carrying either the NOS cDNA (AdCMVceNOS) or no cDNA (AdRR5) via the Infiltrator. Local gene transfer efficiency and bioactivity of recombinant protein were assessed after 4 days. Indices of restenosis were evaluated by computerized planimetry on coronary artery sections prepared 28 days after angioplasty. Adenoviral vectors permitted efficient gene delivery to medial SMCs and adventitial cells of coronary arteries. Vascular cGMP levels were depressed after angioplasty from 1.30+/-0.42 to 0.33+/-0.20 pmol/mg protein (P<0.05) but were restored after constitutive endothelial (ce) NOS gene transfer to 1.82+/-0.98 pmol/mg (P<0.05 versus injured group and P=NS versus control). The ratio of the neointimal area to the internal elastic lamina fracture length, maximal neointimal thickness, and percent stenosis were all reduced in AdCMVceNOS- versus AdRR5-transduced pigs (0.59+/-0.14 versus 0.80+/-0.19 mm, P=0.02; 0.75+/-0.21 versus 1.04+/-0.25 mm, P=0.019; and 53+/-15% versus 75+/-11%, P=0.006, respectively). Lumen area was significantly larger (0.70+/-0.35 mm2 in AdCMVceNOS versus 0.32+/-0.18 mm2 in AdRR5, P=0.007).

CONCLUSIONS

Percutaneous adenovirus-mediated NOS gene transfer resulted in efficient local overexpression of functional NOS after angioplasty in coronary arteries. Restored NO production in injured coronary arteries significantly reduced luminal narrowing, most likely through a combined effect on neointima formation and on vessel remodeling after angioplasty.