Left ventricular thin-point detection using multidetector spiral computed tomography

Diagnosis and Management of Left Ventricular Perforation During Mapping of Ventricular Tachycardia

BACKGROUND Cardiac perforation leading to cardiac tamponade is one of the possible complications of endocardial mapping during catheter-based ablation procedures. The early diagnosis of catheter-induced perforation is critical for effective management of these patients. We hereby present the diagnosis and management of left ventricular perforation during mapping of ventricular tachycardia in a patient with left ventricular aneurysm. CASE REPORT A 70-year-old man with a history of ischemic heart disease, arterial hypertension, type 2 diabetes mellitus, and obesity was referred to our institution for the ablative treatment of recurrent, sustained monomorphic ventricular tachycardia that was resistant to medication. One particularity was the presence of a left ventricular aneurysm secondary to a non-ST segment elevation myocardial infarction, which was unusual and could increase the risk of cardiac perforation. During left ventricular mapping, several points were acquired in an apparently unusual position and the pericardial location of the mapping catheter was confirmed fluoroscopically. After setting a pericardial pigtail catheter, we successfully finished the ablation procedure using a second ablation catheter. The perforating catheter was thereafter removed by open surgery, and no significant bleeding occurred. The patient did not experience tachycardia during the follow-up period of 29 months. CONCLUSIONS Left ventricular aneurysms might increase the cardiac perforation risk during endocardial mapping in ventricular tachycardia ablation procedures. In patients with this condition, a careful manipulation of the catheters could prevent such complications. The periodic fluoroscopic assessment of the catheter's position is essential for early recognition of the perforation.

"Apical thinning": Relations between myocardial wall thickness and apical left ventricular tracer uptake as assessed with positron emission tomography myocardial perfusion imaging

BACKGROUND

A reduction in left ventricular apical tracer uptake (apical thinning) is frequently observed in myocardial perfusion imaging (MPI), yet its cause remains a matter of debate, particularly in perfusion emission tomography (PET). This analysis sought to determine whether apical thinning in PET-MPI is attributable to true anatomical thinning of the left ventricular apical myocardium.

METHODS AND RESULTS

We retrospectively analyzed 57 patients without any history or signs of apical myocardial infarction who underwent rest PET-MPI with 13N-ammonia and contrast-enhanced cardiac computed tomography (CT). Semi-quantitative normalized percent apical 13N-ammonia uptake at rest, myocardial blood flow (MBF), and k2 wash-out rate constants were compared to apical myocardial wall thickness measurements derived from CT and base-to-apex gradients were calculated. Apical thinning was found in 93% of patients and in 74% when analysis of normalized apical tracer uptake was confined to end-systole. No significant correlation was found between apical myocardial thickness and apical tracer uptake (r = - 0.080, P = .553), MBF (r = - 0.211, P = .115), or k2 wash-out rate (r = - 0.023, P = .872), nor between apical myocardial thickness and any gradients. A statistically significant but small difference in apical myocardial thickness was observed in patients with moderately to severely reduced apical tracer uptake vs patients with normal to mildly reduced uptake (4.3 ± 0.7 mm vs 4.7 ± 0.7 mm; P = .043).

CONCLUSIONS

Apical thinning is a highly prevalent finding during 13N-ammonia PET-MPI that is not solely attributable to true anatomical apical wall thickness or the partial volume effect. Other factors that yet need to be identified seem to have a more prominent impact.

Revisiting the prevalence and diversity of localized thinning of the left ventricular apex

BACKGROUND

The left ventricular apex commonly has a paper-thin structure. However, available data about its structure are limited to variable samples, methodologies, and results.

OBJECTIVE

To investigate the structural anatomy of the left ventricular apex using living heart datasets with the latest computed tomography scanner.

METHODS

One hundred thirty-one consecutive patients (median age, 73 years; 58% men) who underwent cardiac computed tomography were retrospectively analyzed. Patients with severe aortic stenosis were analyzed separately. Thickness and diameters of the thinnest part of the left ventricular apex during mid-diastole were measured using orthogonal multiplanar reconstruction images. The area of thinning was estimated using the formula for the ellipse.

RESULTS

In 88 patients without severe aortic stenosis, the median thickness of the thinnest area of the left ventricular apex was only 0.9 mm. Among them, 74%, 99%, and 100% of cases displayed a left ventricular apex thinner than 1.0, 3.0, and 5.0 mm, respectively. The median area of the thinnest region was 5.6 mm² . In 43 patients with severe aortic stenosis, the median thickness of the thinnest area of the left ventricular apex was 1.2 mm. Among them, 51%, 93%, and 100% of cases displayed a left ventricular apex thinner than 1.0, 3.0, and 5.0 mm, respectively. The median area of the thinnest region was 3.9 mm² .

CONCLUSIONS

Localized thinning of the left ventricular apex is unexceptional, regardless of aortic stenosis with concentric left ventricular hypertrophy, thus highlighting the need for a reappreciation of this feature to avoid inadvertent catastrophic complications.

Nonequilibrium arrhythmic states and transitions in a mathematical model for diffuse fibrosis in human cardiac tissue

We present a comprehensive numerical study of spiral-and scroll-wave dynamics in a state-of-the-art mathematical model for human ventricular tissue with fiber rotation, transmural heterogeneity, myocytes, and fibroblasts. Our mathematical model introduces fibroblasts randomly, to mimic diffuse fibrosis, in the ten Tusscher-Noble-Noble-Panfilov (TNNP) model for human ventricular tissue; the passive fibroblasts in our model do not exhibit an action potential in the absence of coupling with myocytes; and we allow for a coupling between nearby myocytes and fibroblasts. Our study of a single myocyte-fibroblast (MF) composite, with a single myocyte coupled to fibroblasts via a gap-junctional conductance , reveals five qualitatively different responses for this composite. Our investigations of two-dimensional domains with a random distribution of fibroblasts in a myocyte background reveal that, as the percentage of fibroblasts increases, the conduction velocity of a plane wave decreases until there is conduction failure. If we consider spiral-wave dynamics in such a medium we find, in two dimensions, a variety of nonequilibrium states, temporally periodic, quasiperiodic, chaotic, and quiescent, and an intricate sequence of transitions between them; we also study the analogous sequence of transitions for three-dimensional scroll waves in a three-dimensional version of our mathematical model that includes both fiber rotation and transmural heterogeneity. We thus elucidate random-fibrosis-induced nonequilibrium transitions, which lead to conduction block for spiral waves in two dimensions and scroll waves in three dimensions. We explore possible experimental implications of our mathematical and numerical studies for plane-, spiral-, and scroll-wave dynamics in cardiac tissue with fibrosis.

Investigation of cardiomyopathy using cardiac magnetic resonance imaging part 1: Common phenotypes

Cardiac magnetic resonance imaging (CMRI) has emerged as a useful tertiary imaging tool in the investigation of patients suspected of many different types of cardiomyopathies. CMRI sequences are now of a sufficiently robust quality to enable high spatial and temporal resolution image acquisition. This has led to CMRI becoming an effective non-invasive imaging gold standard for many cardiomyopathies. In this 2-part review, we outline the typical sequences used to image cardiomyopathy, and present the imaging spectrum of cardiomyopathy. Part 1 focuses on the current classification of cardiomyopathy, basic CMRI sequences used in evaluating cardiomyopathy and the imaging spectrum of common phenotypes.

Cause of apical thinning on attenuation-corrected myocardial perfusion SPECT

OBJECTIVES

Decreases in apical and apex activities - namely, 'apical thinning' - are a well-known phenomenon in attenuation-corrected (AC) myocardial perfusion. The aim of this study was to compare actual myocardial thickness derived from a multidetector-row computed tomography with AC myocardial perfusion count from a hybrid single-photon emission computed tomography/computed tomography to investigate the cause of apical thinning.

METHODS

We enrolled 21 participants with a low likelihood of coronary artery disease (mean age 65 ± 21 years, 13 men) from 185 consecutive patients and 11 healthy volunteers, who independently underwent ⁹⁹mTc-sestamibi single-photon emission computed tomography/computed tomography and 64-slice multidetector-row computed tomography scans. AC and non-AC myocardial perfusion counts and thickness were measured on the basis of a 17-segment model and averaged at the apex, apical, mid, and basal walls.

RESULTS

Myocardial thickness at the apex was significantly thinner than that at the apical and mid walls (5.1 ± 1.3, 7.3 ± 1.3, and 9.9 ± 2.4 mm, respectively; P<0.005). AC count at the apex was significantly lower than that at the apical and mid regions (76.0 ± 5.5, 82.8 ± 4.7, and 85.6 ± 3.8, respectively; P<0.002). Moderate relationship was observed between myocardial thickness and AC count (y=-10.5 + 0.22x, r=0.54, P<0.0001. No relationship was found between thickness and non-AC count (r=0.16, P=0.263).

CONCLUSION

The low apex and apical counts were caused by anatomical thinning of the myocardium in AC myocardial perfusion imaging. Attenuation correction provided an accurate relationship between myocardial count and thickness because of the partial volume effect.

Left ventricular apical diseases

There are many disorders that may involve the left ventricular (LV) apex; however, they are sometimes difficult to differentiate. In this setting cardiac imaging methods can provide the clue to obtaining the diagnosis. The purpose of this review is to illustrate the spectrum of diseases that most frequently affect the apex of the LV including Tako-Tsubo cardiomyopathy, LV aneurysms and pseudoaneurysms, apical diverticula, apical ventricular remodelling, apical hypertrophic cardiomyopathy, LV non-compaction, arrhythmogenic right ventricular dysplasia with LV involvement and LV false tendons, with an emphasis on the diagnostic criteria and imaging features.

Scroll-wave dynamics in human cardiac tissue: lessons from a mathematical model with inhomogeneities and fiber architecture

Cardiac arrhythmias, such as ventricular tachycardia (VT) and ventricular fibrillation (VF), are among the leading causes of death in the industrialized world. These are associated with the formation of spiral and scroll waves of electrical activation in cardiac tissue; single spiral and scroll waves are believed to be associated with VT whereas their turbulent analogs are associated with VF. Thus, the study of these waves is an important biophysical problem. We present a systematic study of the combined effects of muscle-fiber rotation and inhomogeneities on scroll-wave dynamics in the TNNP (ten Tusscher Noble Noble Panfilov) model for human cardiac tissue. In particular, we use the three-dimensional TNNP model with fiber rotation and consider both conduction and ionic inhomogeneities. We find that, in addition to displaying a sensitive dependence on the positions, sizes, and types of inhomogeneities, scroll-wave dynamics also depends delicately upon the degree of fiber rotation. We find that the tendency of scroll waves to anchor to cylindrical conduction inhomogeneities increases with the radius of the inhomogeneity. Furthermore, the filament of the scroll wave can exhibit drift or meandering, transmural bending, twisting, and break-up. If the scroll-wave filament exhibits weak meandering, then there is a fine balance between the anchoring of this wave at the inhomogeneity and a disruption of wave-pinning by fiber rotation. If this filament displays strong meandering, then again the anchoring is suppressed by fiber rotation; also, the scroll wave can be eliminated from most of the layers only to be regenerated by a seed wave. Ionic inhomogeneities can also lead to an anchoring of the scroll wave; scroll waves can now enter the region inside an ionic inhomogeneity and can display a coexistence of spatiotemporal chaos and quasi-periodic behavior in different parts of the simulation domain. We discuss the experimental implications of our study.

Left ventricular apical thinning as normal anatomy

OBJECTIVE

Apical thinning of the left ventricular myocardium has been described by anatomists as a normal feature. Nonetheless, it does not appear in most anatomic atlases. We investigated its presence in healthy patients and patients with left ventricular hypertrophy using coronary computed tomographic arteriography (CCTA).

METHODS

Sixty-four patients without a history of cardiac disease and 8 patients with left ventricular hypertrophy were imaged using coronary computed tomographic arteriography.

RESULTS

All 64 patients had a focus of myocardial thinning at the left ventricular apex (mean, 1.2 mm [SD, 1.1 mm]). Its average span in the oblique coronal plane was 4.4 mm (2.9 mm), corresponding to a median area of 14.3 mm2 with an interquartile range of 3.9 to 31.6. The focus faced 4.8 degrees (5.9 degrees) toward the diaphragmatic side of the apex. The 8 hypertrophied hearts also had a zone of apical thinning. In a subset of 12 patients in whom functional data were analyzed, this focus did not thicken or move over the cardiac cycle.

CONCLUSIONS

A zone of substantial thinning of the left ventricular apex is a normal anatomic feature.