Morphology of the mural and commissural atrioventricular junction of the mitral valve.

OBJECTIVE: This study investigates mitral annular disjunctions (MAD) in the atrial wall-mitral annulus-ventricular wall junction along the mural mitral leaflet and commissures. METHODS: We examined 224 adult human hearts (21.9% females, 47.9±17.6 years) devoid of cardiovascular diseases (especially mitral valve disease). These hearts were obtained during forensic medical autopsies conducted between January 2018 and June 2021. MAD was defined as a spatial displacement (≥2 mm) of the leaflet hinge line towards the left atrium. We provided a detailed morphometric analysis (disjunction height) and histological examination of MADs. RESULTS: MADs were observed in 19.6% of all studied hearts. They appeared in 12.1% of mural leaflets. The P1 scallop was the primary site for disjunctions (8.9%), followed by the P2 scallop (5.4%) and P3 scallop (4.5%). MADs were found in 9.8% of all superolateral and 5.8% of all inferoseptal commissures. The average height for leaflet MADs was 3.0±0.6 mm, whereas that for commissural MADs was 2.1±0.5 mm (p<0.0001). The microscopical arrangement of MADs in both the mural leaflet and commissures revealed a disjunction shifted towards left atrial aspect, filled with connective tissue and covered by elongated valve annulus. The size of the MAD remained remarkably uniform and showed no correlation with other anthropometric factors (all p>0.05). CONCLUSIONS: In the cohort of the patients with healthy hearts, MAD is present in about 20% of all studied hearts. The MADs identified tend to be localised, confined to a single scallop. Moreover, MADs in the commissures are notably smaller than those in the mural leaflet.

Pulmonary valve morphometry revisited: Clinical implications for valvular and supravalvular interventions.

In this cadaver-based study, we aimed to present a novel approach to pulmonary valve (PV) anatomy, morphometry, and geometry to offer comprehensive information on PV structure. The 182 autopsied human hearts were investigated morphometrically. The largest PV area was seen for the coaptation center plane, followed by basal ring and the tubular plane (626.7 ± 191.7 mm2 vs. 433.9 ± 133.6 mm2 vs. 290.0 ± 110.1 mm2 , p < 0.001). In all leaflets, fenestrations are noted and occur in 12.5% of PVs. Only in 31.3% of PVs, the coaptation center is located in close vicinity of the PV geometric center. Similar-sized sinuses were found in 35.7% of hearts, in the remaining cases, significant heterogeneity was seen in size. The mean sinus depth was: left anterior 15.59 ± 2.91 mm, posterior: 16.04 ± 2.82 mm and right anterior sinus: 16.21 ± 2.81 mm and the mean sinus height: left anterior 15.24 ± 3.10 mm, posterior: 19.12 ± 3.79 mm and right anterior sinus: 18.59 ± 4.03 mm. For males, the mean pulmonary root perimeters and areas were significantly larger than those for females. Multiple forward stepwise regression model showed that anthropometric variables might predict the coaptation center plane (sex, age, and heart weight; R2  = 33.8%), tubular plane (sex, age, and BSA; R2  = 20.5%) and basal ring level area (heart weight and sex; R2  = 17.1%). In conclusion, the largest pulmonary root area is observed at the coaptation center plane, followed by the basal ring and tubular plane. The PV geometric center usually does not overlap valve coaptation center. Significant heterogeneity is observed in the size of sinuses and leaflets within and between valves. Anthropometric variables may be used to predict pulmonary root dimensions.

Topographical anatomy of the right atrial appendage vestibule and its isthmuses.

INTRODUCTION: The right atrial appendage (RAA) vestibule is an area located in the right atrium between the RAA orifice and the right atrioventricular valve annulus and may be a target for invasive transcatheter procedures. METHODS AND RESULTS: We examined 200 autopsied human hearts. Three isthmuses (an inferior, a middle, and a superior isthmus) were detected. The average length of the vestibule was 67.4 ± 10.1 mm. Crevices and diverticula were observed within the vestibule in 15.3% of specimens. The isthmuses had varying heights: superior: 14.0 ± 3.4 mm, middle: 11.2 ± 3.1 mm, and inferior: 10.1 ± 2.7 mm (p < .001). The superior isthmus had the thickest atrial wall (at midlevel: 16.7 ± 5.6 mm), the middle isthmus had the second thickest wall (13.5 ± 4.2 mm), and the inferior isthmus had the thinnest wall (9.3 ± 3.0 mm; p < .001). This same pattern was observed when analyzing the thickness of the adipose layer (superior isthmus had a thickness of 15.4 ± 5.6 mm, middle: 11.7 ± 4.1 mm and inferior: 7.1 ± 3.1 mm; p < .001). The average myocardial thickness did not vary between isthmuses (superior isthmus: 1.3 ± 0.5 mm, middle isthmus: 1.8 ± 0.8 mm, inferior isthmus: 1.6 ± 0.5 mm; p > .05). Within each isthmus, there were variations in the thickness of the entire atrial wall and of the adipose layer. These were thickest near the valve annulus and thinnest near the RAA orifice (p < .001). The thickness of the myocardial layer followed an inverse trend (p < .001). CONCLUSIONS: This study was the first to describe the detailed topographical anatomy of the RAA vestibule and that of its adjoining isthmuses. The substantial variability in the structure and dimensions of the RAA isthmuses may play a role in planning interventions within this anatomic region.

Anatomy of the left atrial ridge (coumadin ridge) and possible clinical implications for cardiovascular imaging and invasive procedures.

BACKGROUND: The left atrial ridge is a structure located in the left atrium between the left-sided pulmonary veins ostia and the orifice of the left atrial appendage. Since it was commonly misdiagnosed as a thrombus, the ridge is also known as the "coumadin" or "warfarin" ridge. The left atrial ridge is a potential source of arrhythmias and can be an obstacle in ablation procedures. This study aimed to provide information about the occurrence and spatial morphometric characteristics of the left atrial ridge. METHODS AND RESULTS: The macroscopic morphology of the left atrial ridge was assessed in 200 autopsied human hearts. The ridge was observed in 59.5% of specimens and was absent in the remaining 40.5% of cases. The mean length of the ridge was 22.4 ± 5.1 mm. It was wider at its inferior sector when compared to its superior sector (9.1 ± 5.0 vs 7.9 ± 3.2 mm; P = .028). The total wall thickness measured at the cross section of the ridge was significantly larger in the inferior than in superior sector (6.2 ± 3.5 vs 4.3 ± 1.8 mm; P < .001), although the myocardial thickness was significantly larger at the superior sector (3.1 ± 1.4 vs 1.9 ± 0.9 mm in inferior sector, P < .001). CONCLUSION: The left atrial ridge is a variable structure, present in 59.5% of humans. The ridge is significantly wider and thicker at its inferior sector, although the actual myocardial layer present within the ridge is thinner at this location. Knowledge about the left atrial ridge morphology is key in avoiding unnecessary interventions or complications during invasive procedures.

Topographic characteristics of the left atrial medial isthmus.

BACKGROUND: The purpose of this study was to provide detailed topography of the left atrial medial isthmus (situated between the right inferior pulmonary vein ostium and the medial part of the mitral annulus). METHODS: Two hundred human hearts (Caucasian, 22.5% females, 48.7 ± 4.9 years old) were investigated. RESULTS: The mean length of the medial isthmus was 42.4 ± 8.6 mm. Additionally, the medial isthmus line was divided by the oval fossa into three sections with equal mean lengths (upper: 14.2 ± 7.2 vs middle: 14.1 ± 6.1 vs lower: 14.9 ± 4.6 mm; P > .05). The left upper section of the atrial wall was thinner than the lower section (2.5 ± 1.1 vs 3.4 ± 1.6 mm; P < .0001). This study noted three separate spatial arrangements of the isthmus line. Type I (54.5%) had an oval fossa located outside the isthmus line; type II (32.5%) had an oval fossa crossed by the isthmus line, and type III (13.0%) had an oval fossa rim located tangentially to the isthmus line. In 68.5% of the examined specimens, the isthmus area had a smooth surface. Conversely, the remaining 31.5% had additional structures within its borders such as diverticula, recesses, and tissue bridges. CONCLUSION: This study is the first to describe the morphometric and topographical features of the left atrial medial isthmus. Interventions within the medial isthmus line should be performed cautiously, especially when they are transected by the oval fossa (32.5%). Careful navigation of the area is also recommended due to the possibility of existent additional structures. The latter could lead to catheter entrapment during ablation procedures.

Fixative properties of honey solutions as a formaldehyde substitute in cardiac tissue preservation.

OBJECTIVES: To evaluate the properties of natural sweetener solutions in whole organ preservation and assess their influence on the dimension, weight and shape of cardiac tissue samples in stated time intervals, up to a one-year period of observation. BACKGROUND: Tissue fixation is essential for biological sample examination. Many negative toxic effects of formaldehyde-based fixatives have forced us to seek alternatives for formaldehyde based solutions. It has been demonstrated that natural sweeteners can preserve small tissue samples well and that these solutions can be used in histopathological processes. However, their ability to preserve whole human organs are unknown. METHODS: A total of 30 swine hearts were investigated. Three study groups (n = 10 in each case) were formed and classified on the type of fixative: (1) 10% formaldehyde phosphate-buffered solution (FPBS), (2) 10% alcohol-based honey solution (ABHS), (3) 10% water-based honey solution (WBHS). Samples were measured before fixation and in the following time points: 24 hours, 72 hours, 168 hours, 3 months, 6 months and 12 months. RESULTS: The WBHS failed to preserve heart samples and decomposition of tissues was observed one week after fixation. In half of the studied parameters, the ABHS had similar modifying tendencies as compared to FPBS. e overall condition of preserved tissue, weight, left ventricular wall thickness, right ventricular wall thickness and the diameter of the papillary muscle differed considerably. CONCLUSIONS: The ABHS may be used as an alternative fixative for macroscopic studies of cardiac tissue, whereas the WBHS is not suited for tissue preservation.

The influence of fixation on the cardiac tissue in a 1-year observation of swine hearts.

AIM: The aim of this study was to investigate the influence of formaldehyde-based fixation on dimension, weight and shape of cardiac tissue during a 1-year observation. MATERIALS AND METHODS: Seven measuring sites were permanently marked in 40 swine hearts prior to fixation. Four study groups (n = 10 each) were assembled that differed only in concentration and the type of fixative. The fixatives were 2%, 4% or 10% formaldehyde phosphate-buffered solution (FPBS) and alcoholic formalin. The samples were measured before fixation and then after fixation at 1 week, 3, 6 and 12 months. RESULTS: At the 3-month point, the 10% FPBS had caused significant changes in the smallest number of parameters, while the 2% FPBS affected the greatest number of dimensions. The most significant changes included chordae tendineae shrinkage and an increase in muscle thickness. After 6 months, the most significant changes were observed in 2% and 4% FPBSs and were also mainly associated with an increase in muscle thickness and chordae tendineae shrinkage. 1-year preservation compared to the baseline showed the most significant changes in muscle tissue thickness and hearth weight. The artery diameter decreased in long-term fixation in every tested solution. For atrial and angle measurements, 4% FPBS caused most significant changes among investigated fixatives. CONCLUSIONS: In all tested solutions, long-term fixation significantly changed cardiac tissue dimension compared to the nonpreserved samples. Short-term to 1-year fixation changes are smaller, but they should not be neglected. Different fixatives should be used depending on the character of the planned measurements.

Spatial relationship of blood vessels within the mitral isthmus line.

Aims: The aim of this study was to assess the spatial relationship of blood vessels and the thickness of the atrial wall within the mitral isthmus line. Methods and results: A total of 200 randomly selected autopsied adult human hearts (Caucasian) were examined. The mitral isthmus line was cut longitudinally and the thickness of the left atrial wall was measured. The blood vessels within the isthmus were identified and their relationship with the endocardial surface (ES), mitral annulus (MA), and the left inferior pulmonary vein (LIPV) ostium was assessed. The mean myocardial thickness in the upper, middle, and lower 1/3 of the mitral isthmus section were 1.9 ± 1.0, 3.0 ± 1.5, and 2.7 ± 1.3 mm, respectively. The great cardiac vein (GCV) was present within the isthmus in 98.0%, the left circumflex artery (LCx) in 57.0%, and the Marshall vein in 35.0% of all hearts. The GCV was located 4.5 ± 2.2 mm from the ES, 7.3 ± 5.3 mm from the MA, and 24.3 ± 7.3 mm from the LIPV. The LCx was situated 3.8 ± 2.3 mm from the ES, 7.9 ± 5.1 mm from the MA, and 25.3 ± 8.0 mm from the LIPV. We were able to detect eight different patterns of GCV and LCx mutual arrangement within the mitral isthmus line. Conclusion: The myocardium is the thinnest in the upper 1/3 sector, and the blood vessels are mainly located in the middle and lower 1/3. In 49.1%, the LCx is situated at a distance of less than 3 mm from the ES. In 55.3%, the LCx is located between the GCV and ES of the left atrium.

Persistent left superior vena cava.

Persistent left superior vena cava (PLSVC) is the most common congenital malformation of thoracic venous return and is present in 0.3 to 0.5% of individuals in the general population. This heart specimen was dissected from a 35-year-old male cadaver whose cause of death was determined as non-cardiac. The heart was examined and we found a PLSVC draining into the coronary sinus. The right superior vena cava was present with a small-diameter ostium. An anomalous pulmonary vein pattern was observed; there was a common trunk to the left superior and left inferior pulmonary veins (diameter 17.8 mm) and an additional middle right pulmonary vein (diameter 2.7 mm) with two classic right pulmonary veins. The PLSVC draining into the coronary sinus had led to its enlargement, which could have altered the cardiac haemodynamics by significantly reducing the size of the left atrium and impeding its outflow via the mitral valve.

Penetration of formaldehyde based fixatives into heart.

OBJECTIVES: To investigate the penetration depth of formaldehyde-based fixatives into cardiac muscle samples over the course of fixation. BACKGROUND: Fixation is the essential step in anatomical studies. However, very little is known about penetration of most common fixatives into cardiac tissue. METHODS: A total of 40 heart samples were investigated. 4 study groups (n=10 in each case) were formed in such manner they differed only in concentration and type of fixative (1) - 2% formaldehyde phosphate-buffered solution (FPBS); (2) - 4% FPBS (formalin); (3) - 10% FPBS; (4) - alcoholic formalin. Samples were measured before fixation and in the following time points: 24 hours, 72 hours, 168 hours. RESULTS: The penetration depth differed significantly among studied fixatives (p<0.0001). 100% penetration occurred in all samples after 72 hours in alcoholic formalin solution and after 168 hours in 10% FPBS. After alcoholic formalin fixation, the tissue is more brittle and sub-epicardial blisters were observed in some cases. CONCLUSIONS: Alcoholic formalin solution is the fastest fixative among the studied ones, however it has several adverse effects on tissue structure. It was found that 10% FPBS is the best and a relatively fast fixative for cardiac morphometric studies.

Anatomic characteristics of the mitral isthmus region: The left atrial appendage isthmus as a possible ablation target.

The mitral isthmus is a part of the postero-inferior area of the lateral left atrial wall located between the mitral annulus and the left inferior pulmonary vein ostium. Linear ablation lesions are created within the mitral isthmus for the invasive treatment of left atrial arrhythmias. However, the anatomy of this region is not fully understood. The aim of this study has been to provide a detailed morphometric description of the mitral isthmus region and to propose another possible isthmus within the investigated heart area that may serve as a potential new ablation target. Two hundred autopsied, non-atrial fibrillation hearts (23.5% deriving from females) whose donors were a mean of 47.6±17.6years old were investigated. We macroscopically assessed the anatomy of the postero-inferior area of the lateral left atrial wall. The mean mitral isthmus length was 28.8±7.0mm and was significantly longer than the left atrial appendage (LAA) isthmus (14.2±4.8mm) (p=.00). The distance between the LAA orifice and the left inferior pulmonary vein ostium (18.4±4.8mm) was longer than the LAA isthmus (p=.00) and shorter than the mitral isthmus (p=.00). The LAA isthmus was longer in hearts with a common left pulmonary vein (p=.037). In 65.5% of all cases the area between the right and left mitral isthmus lines was completely smooth. In the remaining hearts, crevices and diverticula (18.0%), intertrabecular recesses (7.0%), trabecular bridges (3.5%), or co-existence of these structures (6%) could be observed. The LAA isthmus line was smooth in 95.5% of all cases, with only small crevices in the remaining 4.5%. In conclusion, regardless of the anatomical variants of the left-sided pulmonary veins, the mitral isthmus area is quite uniform in size. The LAA isthmus is considerably shorter than the mitral isthmus. The mitral isthmus line has many unwanted structures that may entrap the catheter, which is not the case for the LAA isthmus. We proposed the LAA isthmus line for potential clinical use.

Clinical Anatomy of the Cavotricuspid Isthmus and Terminal Crest.

The aim of this study was to provide useful information about the cavotricuspid isthmus (CTI) and surrounding areas morphology, which may help to plan CTI radio-frequency ablation. We examined 140 autopsied human hearts from Caucasian individuals of both sexes (29.3% females) with a mean age of 49.1±17.2 years. We macroscopically investigated the lower part of the right atrium, the CTI, the inferior vena cava ostium and the terminal crest. The paraseptal isthmus (18.5±4.0 mm) was significantly shorter than the central isthmus (p<0.0001), and the central isthmus (24.0±4.2 mm) was significantly shorter than the inferolateral isthmus (29.3±4.9 mm) (p<0.0001). Heart weight was positively correlated with all isthmus diameters. Three different sectors of CTI were distinguished: anterior, middle and posterior. The middle sector of the CTI presented a different morphology: trabeculae (N = 87; 62.1%), intertrabecular recesses (N = 35; 25.0%) and trabecular bridges (N = 18; 12.9%). A single sub-Eustachian recess was present in 48.6% of hearts (N = 68), and a double recess was present in 2.9% of hearts (N = 4) with mean depth = 5.6±1.8mm and diameter = 7.1±3.4mm. The morphology of the distal terminal crest was varied; 10 patterns of the distal terminal crest ramifications were noted. There were no statistically significant differences in any of the investigated CTI parameters between groups with different types of terminal crest ramifications. The presence of intertrabecular recesses (25.0%), trabecular bridges (12.9%) and sub-Eustachian recesses (48.6%) within the CTI can make ablation more difficult. We have presented the macroscopic patterns of final ramifications of the terminal crest within the quadrilateral CTI area.

Atrial septal pouch - Morphological features and clinical considerations.

BACKGROUND: The atrial septal pouch (SP) is a new anatomical entity within the interatrial septum. The left-sided SP may be the source of thrombus and contribute to ischemic stroke. The aim of this study was to provide a detailed morphometric description of the SP. METHODS: Two hundred autopsied hearts (23% deriving from females) with a mean age of 46.7±19.1years were investigated. We assessed the morphology of the interatrial septum. We obtained measurements and casts of the SPs, and we conducted histological staining of the left-sided SPs. RESULTS: Patent foramen ovale was observed in 25% of hearts. We found a left SP in 41.5%, right in 5.5% and a double SP in 5.5% of hearts. We found the patent foramen ovale (PFO) more often in younger hearts, and the SP and smooth septum were more prevalently found in older hearts (p=.0023). The mean volume of the left-sided SP was 0.31±0.11ml, which represented 13.6±9.4% (range: 3.1-44.9%) of the left atrial appendage volume. The SP shape resembled a cone or a cylinder with some smaller diverticula originating from the main body. The SP free wall was composed of two layers of endocardium, transverse muscle fibers and connective tissue. CONCLUSIONS: A left-sided SP was present in 47% of individuals. The SP arises as a result of PFO channel closure. The anatomy of left-sided SP may promote blood stasis and thrombus formation. The universal formula for SP volume was calculated.