The conditional connexin43G138R mouse mutant represents a new model of hereditary oculodentodigital dysplasia in humans.

Oculodentodigital dysplasia (ODDD) is a dominant negatively inherited disorder with variable but characteristic anomalies of the fingers and toes, eyes, face and teeth, which are caused by mutations in the connexin 43 (Cx43) gene. All mutations analyzed so far have a negative influence on the conductance through gap junctional channels and hemichannels, as well as trafficking of Cx43 protein in transfected cells. In this study, we inserted the human Cx43G138R point mutation into the mouse Cx43 gene and generated mice conditionally expressing this mutation. All ODDD phenotypic manifestations observed in humans, including syndactyly and enamel hypoplasia as well as craniofacial, bone and heart anomalies, were also observed with significant penetrance in Cx43G138R mice. When this mutation was specifically expressed in cardiomyocytes, characteristic alterations in the electrocardiogram and spontaneous arrhythmias were recorded. In vitro studies with Cx43G138R-expressing cells revealed loss of the Cx43 P2 phosphorylation state, which was also absent in the mutated hearts. This loss has previously been associated with gap junctional dysfunction and increased cellular ATP release. The Cx43G138R mutated mice show significantly increased arrhythmogeneity ex vivo in Langendorff experiments with explanted hearts and in vivo in particular under hypoxic conditions. Our results suggest that the increased activity of ATP-releasing channels in Cx43G138R mutated cardiomyocytes may further reduce the already decreased gap junctional communication and thus aggravate arrhythmogenesis in the mouse mutant.

Echocardiographic assessment of global left ventricular function in mice.

Doppler-echocardiographic assessment of cardiovascular structure and function in murine models has developed into one of the most commonly used non-invasive techniques during the last decades. Recent technical improvements even expanded the possibilities. In this review, we summarize the current options to assess global left ventricular (LV) function in mice using echocardiographic techniques. In detail, standard techniques as structural and functional assessment of the cardiovascular phenotype using one-dimensional M-mode echocardiography, two-dimensional B-mode echocardiography and spectral Doppler signals from mitral inflow respective aortal outflow are presented. Further pros and contras of recently implemented techniques as three-dimensional echocardiography and strain and strain rate measurements are discussed. Deduced measures of LV function as the myocardial performance index according to Tei, estimation of the mean velocity of circumferential fibre shortening, LV wall stress and different algorithms to estimate the LV mass are described in detail. Last but not least, specific features and limitations of murine echocardiography are presented. Future perspectives in respect to new examination techniques like targeted molecular imaging with advanced ultrasound contrast bubbles or improvement of equipment like new generation matrix transducers for murine echocardiography are discussed.

Quantitation of myocardial borderzone using reconstructive 3-D echocardiography after chronic infarction in rats: incremental value of low-dose dobutamine.

Myocardial remodeling determines the degree of left ventricular dysfunction and mortality after transmural chronic myocardial infarction (CMI). Noninvasive characterization and quantitation of myocardial borderzone and collagenous scar are therefore parameters of clinical interest. The aims of this study were (i) to measure accuracy of reconstructive 3-D echocardiography (3DE) in scar and myocardial borderzone size assessment and (ii) to investigate the incremental value of low-dose dobutamine stress. 3DE was performed in 14 immunodeficient rats (rnu-rnu, 180-200 g) with anterior CMI 25 d after coronary ligation. Briefly, consecutive parallel short-axis cineloops were obtained electrocardiogram-gated starting from base to the apex. Morphology (mass, surface) and function (contractility, contractile reserve) of different compartments were assessed and correlated with 3-D histomorphometry. Histology was done using picrosirius red for collagen staining. 3DE left ventricular mass correlated closely with histomorphometry (y = 0.89x + 155, p < 0.0001, r = 0.80). Hypo- and akinetic myocardial surface correlated well with borderzone myocardium (y = 0.34x + 17, p = 0.009, r = 0.62) and collagenous scar (y = 1.9x + 4.4, p < 0.0001, r = 0.79), respectively. Extent of abnormal wall motion was closely related to borderzone and scar tissue area (y = 0.82x + 7, p < 0.0001, r = 0.77). 3DE quantitation of borderzone myocardium, but not collagenous scar, was more closely correlated to histomorphometry during inotropic stimulation. Global contractile reserve is positively associated with the size of myocardial borderzone. Regional contractile reserve of borderzone myocardium is not negatively associated with its collagen content. 3DE allows precise quantitation of myocardial borderzone and identification of transmural scar tissue noninvasively. Assessment of contractile reserve improves characterization and estimation of myocardial borderzone after CMI.

Persistence of iatrogenic atrial septal defect after pulmonary vein isolation--an underestimated risk?

BACKGROUND: According to present knowledge, pulmonary vein isolation (PVI) bears a low interventional risk and has a high feasibility. For completion of PVI, left atrial access is achieved via single or double transseptal puncture. We sought to determine the incidence and echocardiographic characteristics of persistent iatrogenic atrial septal defect (iASD) after PVI. Further objectives were to define clinical and periprocedural risk factors for the development of iASD. METHODS: Every patient admitted for PVI at our hospital was screened for eligibility for study participation. Exclusion criteria were inability for undergoing transesophageal echocardiography, preexisting atrial septal defect, open-heart surgery or another transseptal procedure during the follow-up period. Transesophageal echocardiography was performed before PVI and after 9 months. Interatrial shunt was characterized by echocardiographic parameters; right-to-left-shunting (RLS) was quantified by contrast echocardiography. RESULTS: Forty-two patients were included, 27 patients underwent PVI with single transseptal puncture and additional advancement of a second electrophysiologic catheter (group A) 15 patients underwent PVI with double transseptal puncture (group B). In 8 patients of group A, iASD persisted after the follow-up period, including 6 patients with distinct RLS. We saw no iASD in group B (P = .011, CI -0.79 to -0.11). Preprocedural pulmonary artery pressure was significantly higher in patients with iASD and accompanying RLS, compared with patients with iASD and no evidence of RLS (23.75 +/- 0.50 vs 17.59 +/- 5.82, P = .048, CI 0.048-12.27). CONCLUSION: This is the first study that demonstrates a high incidence of long-term persistent iatrogenic atrial septal defect with RLS after PVI. All interatrial shunts occurred after single transseptal puncture with passage of 2 electrophysiologic catheters into the left atrium. Increased preprocedural pulmonary artery pressure seems to promote the occurrence of RLS across iASD.

Impact of previous myocardial infarction on the incremental value of myocardial contrast to two-dimensional supine bicycle stress echocardiography in evaluation of coronary artery disease.

BACKGROUND: If compared to two-dimensional echocardiography (2DE), myocardial contrast echocardiography (MCE) improves detection of coronary artery disease (CAD) during pharmacological stress, but data on MCE vs. 2DE during supine bicycle stress is limited. Although previous myocardial infarction (MI) influences sensitivity of 2DE, its effect on MCE has not been evaluated. OBJECTIVES: The study sought to determine the incremental benefit of MCE over 2DE for evaluation of CAD during supine bicycle stress and to assess the impact of previous MI on diagnostic values of both methods. METHODS: We studied 103 consecutive patients scheduled for coronary angiography. Prior to coronary angiography, all patients underwent supine bicycle stress. 2DE and MCE were performed during this stress test. The diagnosis of obstructive CAD (> or =50% stenosis) was based on the presence of inducible wall motion and perfusion abnormalities. RESULTS: Quantitative coronary angiography revealed > or =50% stenosis in 53 of 77 patients without previous MI and in 21 of 26 patients with previous MI. If compared to 2DE, MCE was more sensitive (68% vs. 86%; p<0.001) and more accurate (73% vs. 86%; p < 0.001) to detect > or =50% stenosis. In patients without previous MI, 2DE and MCE yielded sensitivity of 65% and 85% (p < 0.01) and accuracy of 71% and 85% (p < 0.01), whereas in patients with previous MI sensitivity was 79% and 90% (p=NS) and accuracy 79% and 88% (p = NS), respectively. CONCLUSIONS: MCE enhances sensitivity and accuracy of 2DE in detection of obstructive CAD during supine bicycle stress. The incremental benefit of MCE is especially present in patients without previous MI.

Functional impact of targeted closed-chest transplantation of bone marrow cells in rats with acute myocardial ischemia/reperfusion injury.

Intramyocardial transplantation of bone marrow-derived stem cells is a potential therapeutic option after myocardial infarction (MI). Intramyocardial administration is invasive but allows efficient and targeted stem cell delivery. Aims of this study were validation of minimal-invasive, echo-guided closed-chest cell transplantation (CTx) of mononuclear (MNC) or mesenchymal stem cells (MSC) and quantification of systolic left ventricular function and assessment of contractile reserve with high-resolution reconstructive 3D-echocardiography (r3D-echo) 3 weeks after CTx. Female Fischer344 rats received syngeneic male MNC, MSC, or medium after myocardial ischemia and reperfusion via echo-guided percutaneous injection (open-chest for control). Left ventricular systolic function was measured and dysfunctional myocardium was quantified with r3D-echo. For investigation of contractile reserve and myocardial viability r3D-echo was additionally conducted during low-dose dobutamine 3 weeks after CTx. Cell persistence after echo-guided CTx was quantified via real-time PCR; scar size was measured histologically. Echo-guided percutaneous CTx was feasible in all animals (n = 30) without periprocedural complications. After 3 weeks, 1.4 +/- 1.1% of transplanted MNC and 1.9 +/- 1.2% of MSC were detected. These numbers were comparable to those after open-chest intramyocardial injection of MNC (0.8 +/- 1.1%; n = 8, p = 0.3). In r3D-echo no functional benefit was associated with CTx after MI and reperfusion. All groups (MNC, MSC, and controls) revealed a significant decrease of dysfunctional myocardium and similar contractile reserve during inotropic stimulation.In conclusion, percutaneous echo-guided closed-chest CTx promises to be an effective and safe approach for CTx in small-animal research. However, intramyocardial CTx of MNC or MSC had no influence on systolic function and contractile reserve after reperfused MI.

Myocardial contrast echocardiography enhances long-term prognostic value of supine bicycle stress two-dimensional echocardiography.

BACKGROUND: The aim of this study was to determine the incremental prognostic value of myocardial contrast echocardiography (MCE) over two-dimensional echocardiography (2DE) in patients undergoing supine bicycle stress. METHODS: Eighty-four patients with known or suspected coronary artery disease who underwent supine bicycle stress with 2DE and MCE (mean age, 58.5 +/- 9.7 years; 68 men) were followed up for 48.3 +/- 8.9 months for cardiac death (n = 1), nonfatal myocardial infarction (n = 9), and revascularization (n = 20). RESULTS: In sequential Cox models, the predictive power of the clinical model was strengthened by 2DE (chi(2) = 7.73 vs 12.92, P = .02) and further improved by MCE (chi(2) = 19.04, P = .01). On multivariate analysis, the only independent follow-up event predictor was ischemia on MCE (hazard ratio, 6.79; 95% confidence interval, 2.02-22.82; P = .001). Among patients with normal results on 2DE, those with normal results on MCE had greater 4.5-year event-free survival than those with abnormal results on MCE (93% vs 69%, P = .01). CONCLUSIONS: MCE enhances the predictive power of supine bicycle stress 2DE and allows the risk stratification of patients with normal results on 2DE.

Real time myocardial contrast echocardiography during supine bicycle stress and continuous infusion of contrast agent. Cutoff values for myocardial contrast replenishment discriminating abnormal myocardial perfusion.

BACKGROUND: Myocardial contrast echocardiography (MCE) is a new imaging modality for diagnosing coronary artery disease (CAD). OBJECTIVE: The aim of our study was to evaluate feasibility of qualitative myocardial contrast replenishment (RP) assessment during supine bicycle stress MCE and find out cutoff values for such analysis, which could allow accurate detection of CAD. METHODS: Forty-four consecutive patients, scheduled for coronary angiography (CA) underwent supine bicycle stress two-dimensional echocardiography (2DE). During the same session, MCE was performed at peak stress and post stress. Ultrasound contrast agent (SonoVue) was administered in continuous mode using an infusion pump (BR-INF 100, Bracco Research). Seventeen-segment model of left ventricle was used in analysis. MCE was assessed off-line in terms of myocardial contrast opacification and RP. RP was evaluated on the basis of the number of cardiac cycles required to refill the segment with contrast after its prior destruction with high-power frames. Determination of cutoff values for RP assessment was performed by means of reference intervals and receiver operating characteristic analysis. Quantitative CA was carried out using CAAS system. RESULTS: MCE could be assessed in 42 patients. CA revealed CAD in 25 patients. Calculated cutoff values for RP-analysis (peak-stress RP >3 cardiac cycles and difference between peak stress and post stress RP >0 cardiac cycles) provided sensitive (88%) and accurate (88%) detection of CAD. Sensitivity and accuracy of 2DE were 76% and 79%, respectively. CONCLUSIONS: Qualitative RP-analysis based on the number of cardiac cycles required to refill myocardium with contrast is feasible during supine bicycle stress MCE and enables accurate detection of CAD.