Adult left ventricular noncompaction: reappraisal of current diagnostic imaging modalities.

Left ventricular noncompaction (LVNC) cardiomyopathy is morphologically characterized by prominent myocardial trabeculations and deep recesses. The precise stage of development and the natural history of the disorder are not fully understood. Studies in heart failure patients demonstrate a high prevalence of myocardial trabeculations, raising the potential diagnosis of LVNC. Given the high prevalence compared with other primary cardiomyopathies, it is unclear whether the myocardial morphology is representative of LVNC or merely epiphenomena associated with increased cardiac pre-load. Imaging modalities including echocardiography and cardiac magnetic resonance imaging facilitate identification and assessment for LVNC; however, current diagnostic criteria are based on small cohorts and are liable to result in an overdiagnosis of LVNC. This review re-evaluates current diagnostic criteria and their potential impact on overdiagnosis of LVNC in low-risk populations.

Virtual fractional flow reserve by coronary computed tomography - hope or hype?

Studies evaluating the diagnostic performance of coronary computed tomography angiography (CTA) are consistent in demonstrating a high negative predictive accuracy, but only a modest positive predictive accuracy for the detection of significant coronary artery disease. Consequentially, there has been a considerable effort made to enhance the diagnostic capability of coronary CTA by developing scanner technology and also post-processing algorithms for coronary stenosis evaluation. Of these new developments, the proposition of being able to measure non-invasive fractional flow reserve by coronary computed tomography angiography (FFRct) has generated much recent interest. Initial reports indicate that the application FFRct not only correlates well with invasive fractional flow reserve but also has the potential to enhance substantially the positive predictive accuracy and overall accuracy of coronary CTA. Although it is theoretically possible to measure FFRct using complex computational fluid dynamics adapted from the aeronautical industry, this approach is likely to face a number of challenges prior to it being accepted into the mainstream as an adjunct to coronary CTA. The aim of the current review is to provide an overview of: 1) the fundamental engineering principles behind computational fluid dynamic modelling of coronary arterial blood flow; 2) the difficulties faced from an engineering perspective in developing a truly representative model; and 3) the challenges this technology is likely to face as it attempts to enter the clinical domain.

Benefits of endocardial and multisite pacing are dependent on the type of left ventricular electric activation pattern and presence of ischemic heart disease: insights from electroanatomic mapping.

BACKGROUND: There is considerable heterogeneity in the myocardial substrate of patients undergoing cardiac resynchronization therapy (CRT), in particular in the etiology of heart failure and in the location of conduction block within the heart. This may account for variability in response to CRT. New approaches, including endocardial and multisite left ventricular (LV) stimulation, may improve CRT response. We sought to evaluate these approaches using noncontact mapping to understand the underlying mechanisms. METHODS AND RESULTS: Ten patients (8 men and 2 women; mean [SD] age 63 [12] years; LV ejection fraction 246%; QRS duration 161 [24] ms) fulfilling conventional CRT criteria underwent an electrophysiological study, with assessment of acute hemodynamic response to conventional CRT as well as LV endocardial and multisite pacing. LV activation pattern was assessed using noncontact mapping. LV endocardial pacing gave a superior acute hemodynamic response compared with conventional CRT (26% versus 37% increase in LV dP/dt(max), respectively; P<0.0005). There was a trend toward further incremental benefit from multisite LV stimulation, although this did not reach statistical significance (P=0.08). The majority (71%) of patients with nonischemic heart failure etiology or functional block responded to conventional CRT, whereas those with myocardial scar or absence of functional block often required endocardial or multisite pacing to achieve CRT response. CONCLUSIONS: Endocardial or multisite pacing may be required in certain subsets of patients undergoing CRT. Patients with ischemic cardiomyopathy and those with narrower QRS, in particular, may stand to benefit.

Multi-site left ventricular pacing as a potential treatment for patients with postero-lateral scar: insights from cardiac magnetic resonance imaging and invasive haemodynamic assessment.

AIMS: Multi-site left ventricular (LV) pacing may be superior to single-site stimulation in correcting dyssynchrony and avoiding areas of myocardial scar. We sought to characterize myocardial scar using cardiac magnetic resonance imaging (CMR). We aimed to quantify the acute haemodynamic response to single-site and multi-site LV stimulation and to relate this to the position of the LV leads in relation to myocardial scar. METHODS: Twenty patients undergoing cardiac resynchronization therapy had implantation of two LV leads. One lead (LV1) was positioned in a postero-lateral vein, the second (LV2) in a separate coronary vein. LV dP/dtmax was recorded using a pressure wire during stimulation at LV1, LV2, and both sites simultaneously (LV1 + 2). Patients were deemed acute responders if ΔLV dP/dtmax was ≥ 10%. Cardiac magnetic resonance imaging was performed to assess dyssynchrony as well as location and burden of scar. Scar anatomy was registered with fluoroscopy to assess LV lead position in relation to scar. RESULTS: LV dP/dtmax increased from 726 ± 161 mmHg/s in intrinsic rhythm to 912 ± 234 mmHg/s with LV1, 837 ± 188 mmHg/s with LV2, and 932 ± 201 mmHg/s with LV1 and LV2. Nine of 19 (47%) were acute responders with LV1 vs. 6/19 (32%) with LV2. Twelve of 19 (63%) were acute responders with simultaneous LV1 + 2. Two of three patients benefitting with multi-site pacing had the LV1 lead positioned in postero-lateral scar. CONCLUSION: Multi-site LV pacing increased acute response by 16% vs. single-site pacing. This was particularly beneficial in patients with postero-lateral scar identified on CMR.

Regional ventricular dynamics during acute coronary occlusion: a comparison of invasive with non-invasive echocardiographic markers to detect and quantify myocardial ischaemia-observations made during off-pump coronary surgery.

OBJECTIVES: To investigate the performance of non-invasive markers used in stress echocardiography to detect the presence and depth of myocardial ischaemia. We therefore sought to compare these non-invasive markers during acute coronary occlusion in humans. METHODS: 27 patients with stable angina and normal LV cavity size were studied during off-pump coronary artery bypass grafting to the left anterior descending coronary artery using transoesophageal echocardiography and simultaneous high fidelity LV pressure. Regional power development of the anterior wall was plotted throughout the cardiac cycle, allowing the measurement of its time course, peak value and time integral (intrinsic work). Regional effective myocardial work was calculated and its reduction during acute occlusion was used as the invasive standard for ischaemic dysfunction. RESULTS: In all patients acute coronary occlusion led to a delay in the onset of regional wall thickening which persisted after aortic valve closure. These time intervals of myocardial thickening had the highest qualitative concordance with the gold standard of a fall in effective work. Regression models identified three significant predictors of the depth of myocardial ischaemia; the interval from Q wave to the onset of regional thickening, duration of post-ejection thickening and peak thickening rate. Objective wall thickening and thinning rates were not significant predictors. CONCLUSIONS: The regional timing of myocardial thickening and peak thickening rate accurately predicted the presence and indicated the depth of local ischaemia during acute coronary occlusion. These markers may complement subjective wall motion scores aimed at predicting the presence of epicardial coronary artery disease. CONDENSED ABSTRACT: We compared non-invasive markers commonly used in stress echocardiography using measurements of the fall in regional myocardial work with coronary occlusion as a standard. 27 patients were studied using transoesophageal echocardiography and simultaneous high fidelity left ventricular pressure during off-pump coronary surgery. Delayed myocardial thickening had the highest qualitative concordance with the gold standard of a fall in effective work, while regression models identified three significant predictors; the interval Q wave to the onset of regional thickening, duration of post-ejection thickening and peak thickening rate. These markers may complement current non-invasive indices of ischaemia during clinical stress testing.

Characteristics of ischaemic human myocardium: a transoesophageal echocardiographic and voltammetric microelectrode study.

Delayed local myocardial power development (primary asynchrony) has been suggested as a marker of ischaemic ventricular dysfunction in humans. However, to prove this, microcirculatory perfusion, microcirculatory oxygenation, and intrinsic mechanical function of the same asynchronous myocardial segment should be studied simultaneously before and after revascularisation. We performed a prospective intraoperative study of 15 patients (age 67 [SD 5] years) at baseline and 30 min after left anterior descending artery grafting. Local tissue perfusion and oxygenation of the anterior left ventricular wall were quantified with a voltammetric microelectrode technique. Transesophageal M-mode echocardiograms and simultaneous high-fidelity left ventricular pressure were measured. Eight patients showed primary asynchrony and 7 did not. Patients with primary asynchrony had local mechanical depression with lower resting values of myocardial work and peak power which increased with surgery. In this group, resting perfusion consistently increased with surgery (32.1 [13] to 54 [31] ml min(-1) 100 g(-1), P < 0.05). In the remaining patients, local work and power were normal, and resting perfusion was consistently higher (90 [9] Ml min(-1) 100 g(-1), P < 0.05 vs primary asynchrony), and fell with surgery. Local tissue oxygen tension was similar in both groups (38 vs 44 mmHg) and did not change with surgery. In patients with chronic coronary artery disease, microcirculatory perfusion, but not pO2, is reduced in regions showing primary asynchrony and impaired mechanical function. Abnormalities in both mechanical function and perfusion normalise within 30 min of revascularisation. These data provide further evidence that primary asynchrony is not only a marker of chronic ischemic ventricular dysfunction, but is associated with a modified contraction pattern in which normal oxygen tension coexists with reduced perfusion.