The anatomy of the septal perforating arteries in normal and congenitally malformed hearts

The Emerging Role of Left Bundle Branch Area Pacing for Cardiac Resynchronisation Therapy

Cardiac resynchronisation therapy (CRT) reduces the risk of heart failure-related hospitalisations and all-cause mortality, as well as improving quality of life and functional status in patients with persistent heart failure symptoms despite optimal medical treatment and left bundle branch block. CRT has traditionally been delivered by implanting a lead through the coronary sinus to capture the left ventricular epicardium; however, this approach is associated with significant drawbacks, including a high rate of procedural failure, phrenic nerve stimulation, high pacing thresholds and lead dislodgement. Moreover, a significant proportion of patients fail to derive any significant benefit. Left bundle branch area pacing (LBBAP) has recently emerged as a suitable alternative to traditional CRT. By stimulating the cardiac conduction system physiologically, LBBAP can result in a more homogeneous left ventricular contraction and relaxation, thus having the potential to improve outcomes compared with conventional CRT strategies. In this article, the evidence supporting the use of LBBAP in patients with heart failure is reviewed.

Defining the distance between the His bundle and first septal perforator: implications for left bundle branch pacing

BACKGROUND

Left bundle branch pacing (LBBP) is a developing method of native conduction pacing, but cases of injury to the septal perforator arteries during implantation have been reported. Knowing the distance between the His bundle and the first septal perforator artery can help operators implant LBBP leads more safely.

METHODS

Using previously performed coronary CT angiography (CCTA) studies, the distance between the His bundle and the first septal perforator was measured.

RESULTS

A total of 50 CCTA studies were included. The mean distance from the His bundle to the first septal perforator (His-SP) along the line connecting the His bundle to the RV apex (His-RV apex) was 27.17 ± 7.7 mm with a range of 13.0 to 44.7 mm. The distance was greater than 2.0 cm in 84% of patients. To standardize this distance among patients with varying cardiac structures, the ratio between the His-SP distance and the His-RV Apex distance was also measured. The mean His-SP:His-RV Apex was 0.302 and the median was 0.298. Eighty-six percent of patients had a ratio of greater than 0.20.

CONCLUSION

Using this information, operators can aim to implant LBBP leads within 2.0 cm of the His bundle or 20% of the distance between the His bundle and the RV apex with minimal risk of causing vascular injury.

The mid-term outcome of interventricular septal hematoma after ventricular septal defect closure

We present the case report of a patient who developed interventricular septal hematoma as a complication during perimembranous ventricular septal defect closure. Although cardiopulmonary bypass was re-established and the hematoma was aspirated, postoperative echocardiography revealed that the hematoma reaccumulated in the interventricular septum. She suffered from low-cardiac-output syndrome for 1 week requiring a large amount of inotropic agents. Postoperative echocardiography revealed that the interventricular septal hematoma gradually disappeared. At 1 year follow-up, ^99mTc-tetrofosmin myocardial single-photon emission computed tomographic revealed myocardial ischemia in the inferior and septal walls. At 4 years follow-up, her cardiac function has gradually improved. She has no symptoms of heart failure with angiotensin-converting enzyme inhibitor and beta-blocker.

Interventricular septal hematoma detected by transesophageal echocardiography after congenital heart surgery in an infant: a case report

Background

Interventricular septal hematoma is an extremely rare complication following congenital heart surgery. During cardiac surgery, interventricular septal hematomas can be detected only by intraoperative transesophageal echocardiography. Here, we report an interesting case of interventricular septal hematoma that was accidentally found in an infant following ventricular septal defect (VSD) closure.

Case presentation

Transesophageal echocardiography images were acquired from a 1-month-old boy after surgical repair of a large (6.5 mm) perimembranous outlet VSD with interventricular septal flattening. Surgical correction was performed with auto-pericardium and 7–0 Prolene sutures. The patient was successfully weaned from cardiopulmonary bypass, and transesophageal echocardiography showed no VSD leakage and good ventricular function. However, approximately 30 min later, two anechoic masses were found within the interventricular septum, which were suspected to be interventricular septal hematomas; the larger mass measured 1.51 \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\times $$\end{document}× 1.48 cm. The swollen interventricular septum showed decreased contractility and compressed both the right and left ventricles. However, there was no change in the size of hematomas or a significant hemodynamic instability for 30 min of observation. Therefore, expecting spontaneous resolution of the hematomas, the interventricular septum was not explored, and the patient was removed from cardiopulmonary bypass. On postoperative day 4, follow-up transthoracic echocardiography revealed thrombi filling the hematomas. The patient was discharged on postoperative day 15 and followed up with regular echocardiographic evaluations.

Conclusions

We describe a unique case of interventricular septal hematoma after VSD closure. Surgical manipulation of perimembranous VSD and injury of the septal perforating artery may contribute to the development of an interventricular septal hematoma. Moreover, conservative treatment and serial echocardiographic evaluation generally show gradual hematoma resolution in hemodynamically stable patients. Pediatric cardiac anesthesiologists should be aware of this rare complication after VSD repair.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40001-021-00552-4.

Interventricular septal haematoma after EXCOR paediatric implantation

A 3.5-kg boy with dilated cardiomyopathy underwent EXCOR left ventricular assist device implantation, which resulted in right ventricular outflow tract obstruction due to the development of an interventricular septal haematoma (IVSH), which required the implantation of an additional right ventricular assist device. Curettage and haemostasis of the IVSH were successfully performed on postoperative day 17. An 11-kg girl with left ventricular non-compaction also underwent EXCOR left ventricular assist device implantation. An IVSH was initially detected on postoperative day 13 without haemodynamic instability. By decreasing the target-activated partial thromboplastin time, the IVSH completely regressed 2 months later.

Aortic root widening: “pro et contra”

In patients with a small aortic annulus, the clinical benefits of aortic valve replacement depend on avoidance of patient-prosthesis mismatch as it is associated with reduced overall survival. Aortic root widening or enlargement is a useful technique to implant larger valve prosthesis to prevent patient-prosthesis mismatch. Posterior annular enlargement is the commonest technique used for aortic root enlargement. Consistent enlargement of the aortic root requires more extensive procedures like Manouguian or Konno-Rastan techniques. The patients commonly selected are younger patients with good life expectancy. However, caution is advised in applying this procedure in elderly patients, patients with heavily calcified annulus and when performing concomitant procedures. There is no definitive conclusion on the best material to use for the reconstruction of aortic annulus and aorta in aortic root enlargement procedures.

Recognition of acute myocardial infarction caused by spontaneous coronary artery dissection of first septal perforator

AIMS 

Spontaneous coronary artery dissection (SCAD) diagnosis is challenging as angiographic findings are often subtle and differ from coronary atherosclerosis. Herein, we describe characteristics of patients with acute myocardial infarction (MI) caused by first septal perforator (S1) SCAD.

METHODS AND RESULTS 

Patients were gathered from SCAD registries at Minneapolis Heart Institute and Vancouver General Hospital. First septal perforator SCAD prevalence was 11 of 1490 (0.7%). Among 11 patients, age range was 38-64 years, 9 (82%) were female. Each presented with acute chest pain, troponin elevation, and non-ST-elevation MI diagnosis. Initial electrocardiogram demonstrated ischaemia in 5 (45%); septal wall motion abnormality was present in 4 (36%). Angiographic type 2 SCAD was present in 7 (64%) patients with S1 TIMI 3 flow in 7 (64%) and TIMI 0 flow in 2 (18%). Initial angiographic interpretation failed to recognize S1-SCAD in 6 (55%) patients (no culprit, n = 5, septal embolism, n = 1). First septal perforator SCAD diagnosis was established by review of initial coronary angiogram consequent to cardiovascular magnetic resonance (CMR) demonstrating focal septal late gadolinium enhancement with corresponding oedema (n = 3), occurrence of subsequent SCAD event (n = 2), or second angiogram showing healed S1-SCAD (n = 1). Patients were treated conservatively, each with ejection fraction >50%.

CONCLUSION 

First septal perforator SCAD events may be overlooked at initial angiography and mis-diagnosed as 'no culprit' MI. First septal perforator SCAD prevalence is likely greater than reported herein and dependent on local expertise and availability of CMR imaging. Spontaneous coronary artery dissection events may occur in intra-myocardial coronary arteries, approaching the resolution limits of invasive coronary angiography.

What is the mid-wall linear high intensity "lesion" on cardiovascular magnetic resonance late gadolinium enhancement?

BACKGROUND

Cardiovascular magnetic resonance (CMR) late gadolinium enhancement (LGE) is a valuable technique for detecting myocardial disorders and fibrosis. However, we sometimes observe a linear, mid-wall high intensity signal in the basal septum in the short axis view, which often presents diagnostic difficulties in the clinical setting. The purpose of this study was to compare the linear, mid-wall high intensity in the basal septum identified by LGE with the anterior septal perforator arteries identified by coronary computed tomography angiography (CorCTA).

METHODS

We retrospectively selected 148 patients who underwent both CorCTA and CMR LGE within 1 year. In the interpretation of LGE, we defined a positive linear high intensity (LHI+) as follows: ① LHI in the basal septum and ② observable for 1.5 cm or more. All other patients were defined as a negative LHI (LHI-). In LHI+ patients, we assessed the correlation between the LHI length and the septal perforator artery length on CorCTA. We also compared the length of the septal perforator artery on CorCTA between LHI+ patients and LHI- patients.

RESULTS

A population of 111 patients were used for further analysis. Among these , there were 55 LHI+ patients and 56 LHI- patients. In LHI+ patients, linear regression analysis revealed that there was a good agreement between LGE LHI and septal perforator arteries by CorCTA in terms of length measurements. The measured length of the anterior septal perforator arteries was significantly shorter in LHI- patients than in LHI+ patients (10 ± 8 mm vs. 21 ± 8 mm; P < 0.05).

CONCLUSIONS

The LHI observed in the basal septum on short axis LGE may reflect contrast enhancement of the anterior septal perforator arteries. It is important to interpret this septal LHI against knowledge of anatomic structure, to avoid misinterpretations of LGE and prevent misdiagnosis.

Myocardial Rupture Secondary to Ventricular Septal Hematoma: A Case Report and Review of Contemporary Literature

Interventricular septal hematoma following congenital cardiac surgery is an uncommon entity. Literature search reveals few cases of interventricular septal hematoma complicating pediatric cardiac surgery. We report a case of interventricular septal hematoma following patch closure of ventricular septal defect, with associated myocardial necrosis and myocardial rupture.

Anatomy of the septal perforating arteries of the heart

The septal perforating arteries of the heart usually branch off from the anterior and inferior interventricular arteries and supply the interventricular septum and the conduction system therein. Since the septal perforating arteries are not directly visible from the outside of the heart, their anatomy and variations might be overlooked. However, the septal perforating arteries have their unique anatomy that needs to be recognized to avoid the damage of the vessels especially during common cardiac procedures such as the coronary artery bypass graft, percutaneous coronary intervention, and aortic valve replacement. A better understanding of these important arteries will help physicians to enhance the overall cardiac care for their patients. Therefore, this article discusses the anatomy, the relationship to the conduction system of the heart and the clinical significance of the septal perforating arteries.

The artery of Mouchet: blood supply of the septomarginal trabecula in 50 human hearts

The septomarginal trabecula is a muscular structure which transmits the right branch of the atrioventricular bundle. It is usually supplied by a branch from the second anterior septal artery. Anastomoses between the right and left coronary arteries may happen on the septomarginal trabecula. They are of great significance in order to prevent ischemia during a myocardial infarction. Surgeries such as Konno's and Ross' procedures implies in knowledge of these vessels anatomy. The coronary arteries of 50 human hearts were injected with latex and subsequentely dissected with the purpose of identifying the arterial branch that supplied the septomarginal trabecula. The trabecular branch arose from the second anterior septal artery in 38% of cases, and the branch arose from the first anterior septal artery in 26%. One of the hearts had its septomarginal trabecula supplied by the conus arteriosus arteryliterature. Anastomoses between the right and left coronary arteries were found inside the septomarginal trabecula. The right branch of the atrioventricular bundle is subject to a great number of clinical conditions and is often manipulated during surgery, thus, the study of the septal branches of the coronary arteries and the trabecular branch is essential.

How should we diagnose and differentiate hearts with double-outlet right ventricle?

Many, if not most, of the controversies regarding the description of the congenitally malformed heart have been resolved over the turn of the 20th century. A group of lesions that remains contentious is the situation in which both arterial trunks, in their greater part, are supported by the morphologically right ventricle. It was considered, for many years, that presence of bilateral infundibulums, or conuses, was a necessity for such a diagnosis. It has now been appreciated that this suggestion founders on many counts. In the first instance, such bilateral infundibulums are to be found in patients with other ventriculo-arterial connections, including the otherwise normal heart. In the second instance, it is clear that such an approach abrogates the important principle now known as the morphological method. This states that entities should be defined in terms of their intrinsic morphology and not on the basis of other variable features. It is now also clear that, when assessed simply on the basis of the ventricular origin of the arterial trunks, a significant number of patients fulfil the criteria for so-called "200%" origin of the trunks from the right ventricle when there is fibrous continuity between the leaflets of the atrioventricular and arterial valves. In this review, we show how attention to the morphology of the channel between the ventricles now provides the key to accurately diagnose the ventriculo-arterial connection in patients with suspected double-outlet right ventricle. This is because, when both arterial trunks arise exclusively or predominantly from the morphologically right ventricle, the outlet septum, of necessity, is itself a right ventricular structure. The channel between the ventricles, therefore, is roofed by the inner heart curvature, whether that structure is fibrous or muscular. Our observations then confirm that it is the attachment of the outlet septum, which itself can be muscular or fibrous, which determines the commitment of the interventricular communication to the subarterial outlets. The interventricular communication itself, when directly committed to the ventricular outlets, opens between the limbs of the septomarginal trabeculation or septal band. The defect is subaortic when the outlet septum is attached to the cranial limb of the trabeculation, subpulmonary when attached to the caudal limb, and doubly committed when attached to the inner heart curvature in the roof of the defect. Non-committed defects are no longer positioned within the limbs of the septomarginal trabeculation. Although readily demonstrable by a skilled echocardiographer, we show how these anatomical features are more easily demonstrated with added accuracy when using CT data sets.

Effectiveness of Alcohol Septal Ablation Versus Transaortic Extended Myectomy in Hypertrophic Cardiomyopathy with Midventricular Obstruction

OBJECTIVES

Investigate the effectiveness of alcohol septal ablation (ASA) and transaortic extended myectomy (TEM) in hypertrophic cardiomyopathy (HCM) with midventricular obstruction (MVO).

BACKGROUND

MVO is less common than subaortic obstruction. Data on the effectiveness of ASA and TEM in MVO are lacking.

METHODS

The clinical profiles of 22 patients undergoing ASA and 37 patients undergoing TEM were compared. No patient had apical aneurysm, abnormal chordae, mitral valve replacement or repair.

RESULTS

Baseline midventricular pressure gradient and symptoms were comparable between the ASA and TEM groups. During follow-up, both groups demonstrated substantial reduction in pressure gradient (the ASA group: 79.7 ± 21.2 mm Hg to 43.7 ± 28.9 mm Hg, P < 0.001; the TEM group: 69.0 ± 23.9 mm Hg to 15.0 ± 16.9 mm Hg, P < 0.001). The reduction in pressure gradient was greater (78.9 ± 18.6% vs. 46.4 ± 33.4%, P < 0.001) and the residual pressure gradient was lower after TEM versus ASA (P < 0.001). Patients with New York Heart Association class III/IV dyspnea decreased from 59.1 to 18.2% (P = 0.022) in the ASA group and from 56.8 to 5.6% (P < 0.001) in the TEM group. Patients with Canadian Cardiovascular Society class III/IV angina decreased from 40.9 to 9.1% (P = 0.016) in the ASA group and from 32.4 to 0% (P < 0.001) in the TEM group.

CONCLUSIONS

While ASA and TEM both improve gradients and symptoms, TEM may provide a more reliable reduction in gradients compared to ASA.

Coronary Arteries in Childhood Heart Disease: Implications for Management of Young Adults

Survival of patients with congenital heart defects has improved dramatically. Many will undergo interventional catheter or surgical procedures later in life. Others will develop atherosclerotic or post-surgical coronary heart disease. The coronary artery anatomy in patients with congenital heart disease differs substantially from that seen in the structurally normal heart. This has implications for diagnostic procedures as well as interventions. The unique epicardial course seen in some defects could impair interpretation of coronary angiograms. Interventional procedures, especially at the base of the heart, risk injuring unusually placed coronary arteries so that coronary artery anatomy must be delineated thoroughly prior to the procedure. In this review, we will describe the variants of coronary artery anatomy and their implications for interventional and surgical treatment and for sudden death during late follow-up in several types of congenital heart defects including: tetralogy of Fallot, truncus arteriosus, transposition of the great arteries, double outlet right ventricle, congenitally corrected transposition of the great arteries and defects with functionally one ventricle. We will also discuss the coronary abnormalities seen in Kawasaki disease.

Electrovectorcardiographic diagnosis of left septal fascicular block: anatomic and clinical considerations

Several publications considering anatomical, histological, pathological, electrocardiographic, vectorcardiographic, and electrophysiologic studies have shown that the left bundle branch splits into three fascicles or in a "fan-like interconnected network" in the vast majority of human hearts. The left His system is trifascicular with a left anterior, a left posterior, and a left septal fascicle (LSF). Consequently, the classic term "hemiblock," to describe the block of one of the fascicles, established several decades ago by the Rosembaum's school, should be updated. Electrovectorcardiographic changes resulting from conduction abnormalities of the left anterior and left posterior fascicles are commonly diagnosed, mainly by their changes in the frontal plane. However, the existence of conduction defects of the LSF remains controversial. The ECG/VCG hallmark of LSF block is prominent anterior QRS forces (PAF) on the horizontal plane. This ECG/VCG phenomena should be distinguished from other conditions that also produce anterior QRS shift in the HP as: normal variants, right ventricular enlargement, misplaced precordial leads, lateral myocardial infarction, right bundle branch block, Wolff-Parkinson-White, obstructive and nonobstructive forms of hypertrophic cardiomyopahty, diastolic left ventricular enlargement, endomiocardial fibrosis, Duchenne muscular dystrophy, and dextroposition. The two highly frequent etiologies of LSFB are ischemia (coronary artery disease (CAD) with critical proximal obstruction of the left anterior descending coronary artery) and, in Latin America, Chagas' cardiomyopathy. The aims of this review are to revise the evidence of the existence of a trifascicular left Hissian system and to help in the ECG/VCG recognition of the LSFB.

Potential implications of the helical heart in congenital heart defects

The anatomic and functional observations made by Francisco Torrent-Guasp, in particular his discovery of the helical ventricular myocardial band (HVMB), have challenged what has been taught to cardiologists and cardiac surgeons over centuries. A literature debate is ongoing, with interdependent articles and comments from supporters and critics. Adequate understanding of heart structure and function is obviously indispensable for the decision-making process in congenital heart defects. The HVMB described by Torrent-Guasp and the potential impact on the understanding and treatment of congenital heart defects has been analyzed in the following settings: embryology, ventriculo-arterial discordance (transposition of great arteries), Ebstein's anomaly, pulmonary valve regurgitation after repair of tetralogy of Fallot, Ross operation, and other congenital heart defects. The common structural spiral feature is only one of the elements responsible for the functional interaction of right and left ventricles, and understanding the form/function relationship in congenital heart defects is more difficult than for acquired heart disease because of the variety and complexity of congenital heart defects. Individuals involved in the care of patients with congenital heart defects have to be stimulated to consider further investigations and alternative surgical strategies.

Anatomy and echocardiography of discordant atrioventricular connections

The most appropriate way of describing the congenital cardiac malformations unified because the atrial chambers are joined across the atrioventricular junctions to morphologically inappropriate ventricles has long been contentious. In the past, the lesions have been described in such arcane terms as mixed levocardia,1 while “ventricular inversion” still retains it currency in some circles. As we will show in this review, the abnormal arrangements at the atrioventricular junctions can be found with various patterns, but most frequently the patients also have the arterial trunks arising from morphologically inappropriate ventricles. This combination is best described as congenitally corrected transposition, and will form the focus of our review. It is salutary to note that, when von Rokitansky gave the first description of this combination,2 one of his illustrations was ideally suited to aid the understanding of modern-day echocardiographers (Fig. 1). We hope to emulate von Rokitansky in our own review.

The anatomy of hearts with double inlet ventricle

In the past, hearts with double inlet ventricle have been amongst the most contentious of congenital cardiac malformations. This is because, although most examples found with this particular atrioventricular connection have one big and one small chamber within the ventricular mass, for many years the variant most frequently encountered, with a dominant left ventricle, was usually described as exhibiting a single ventricle.1With the recognition that, in this particular variant, the small chamber is an incomplete right ventricle, and is never capable of supporting independently the pulmonary circulation, the anatomic situation has now been clarified, as explained in the previous review,2by recognising that the arrangement produces a functionally single ventricle, and that almost always patients with this lesion, if treated surgically, will be converted to the Fontan circulation. Even though, nonetheless, most patients with all variants of double inlet ventricle will likely end up with the Fontan circulation, it remains necessary to identify the functionally significant variants, namely those to be found in ventricular morphology, atrioventricular valvar morphology, ventriculo-arterial connections, and associated malformations.3

Nomenclature of the functionally univentricular heart

Hearts which, at first sight, seem to have a solitary chamber within their ventricular mass have long been the subject of controversy. As difficult as it is to manage these cardiac malformations medically and surgically, it has been at least as challenging, to date, merely to describe and classify them. Even the most commonly used terms, “single ventricle” and “univentricular heart”, spark heated debate. In distant times, when congenitally malformed hearts were pathological curiosities, these entities were described as “cor triloculare biatriale”. Therein lies the beginning of the problem, since when hearts of this type were examined by more enlightened pathologists, such as the great Maude Abbott,1it became plain that the apparently solitary ventricular mass in reality possessed a second, albeit much smaller, chamber. Abbott described this second structure as the “outlet chamber”. This convention of describing a “single ventricle”, albeit with a co-existing “outlet chamber”, that presumably lacked ventricular status, continued throughout the first half of the twentieth century, although it had been recognised by then that hearts could rarely be found with truly solitary ventricles, and these were typically deemed to be common structures. Van Praagh et al.2neatly summarised the problem with this approach when they pointed out that the so-called “single ventricle” possessed two ventricular chambers, whilst the “common ventricle” described the truly solitary arrangement. In their seminal investigation of 1964, Van Praagh et al.2analysed only those hearts unified because of double inlet atrioventricular connection, or alignment. They excluded arbitrarily from their investigation all hearts with atrioventricular valvar atresia, despite the similarity in morphology between many of these latter lesions and the hearts with double inlet.3

The Ross Procedure: New Insights Into the Surgical Anatomy

BACKGROUND

The precise knowledge of regional anatomical details is of utmost importance specially in complex procedures such as the Ross operation. This anatomical study offers a critical approach regarding the advantages, limits, and precautions for this procedure.

METHODS

Using dissection techniques, magnifications up to x6 and nontraditional approaches, 68 fixed normal heart specimens were studied over a 2-year period. The details of surgical relevance such as the boundaries and relations of the pulmonary and aortic roots, their vascularization, and the number and distribution of the septal arteries are described.

RESULTS

The aortic and pulmonary roots include interdependent elements functioning in a coordinated manner and establishing important relations with adjacent structures. Both coronary arteries vascularize the arterial roots. The infundibular branches from the right coronary artery are larger and more constant. The septal arteries establish important relations with the pulmonary infundibulum but their contribution to its vascularization is negligible. In this series, the main septal artery was the second, showing the longest retroinfundibular course. However, no constant relation was found between this vessel and the intraventricular landmarks.

CONCLUSIONS

A novel approach was used by performing nontraditional dissections of the arterial roots and by studying their vascularization The depicted details are useful to the surgeon specializing in the Ross procedure and represent the basis for further research.

Problems with the right ventricular outflow tract: a review of morphologic features and current therapeutic options

Repair of complex malformations that necessitate restoration of continuity between the right ventricle and the pulmonary arteries can now safely be performed with low morbidity and mortality. Major concerns still remain on the long-term outlook for these patients, and about the durability of the different prostheses used to restore that continuity, whether during initial correction or at the time of reintervention for failure of the conduit or pulmonary regurgitation. In this review, we discuss the salient morphologic features of the right ventricular outflow tract, and then focus on the indications for early and late intervention, current therapeutic options, and outcomes.

Morphology of the functionally univentricular heart

Of all the complex malformations that affect the heart, those that have produced the greatest difficulty, over the years, in terms of logical description and classification are the ones with the circulations supported by a functionally univentricular mass. The problems in description stem from the fact that, although the ventricular mass functions as a singular entity, the majority of lesions falling within this category, from the stance of morphology, possess two ventricular chambers. For many years, and indeed, even now in many centres, the hearts are described as being “univentricular”, or alternatively as “single ventricles”. There is still no consensus as to which particular lesions should be included within this “univentricular” category. The paradigm of the group is usually taken as double inlet left ventricle.1In this lesion, the dominant left ventricle is accompanied by a rudimentary second chamber, albeit that arguments continue as to whether the second chamber is an incomplete right ventricle,2or simply an infundibulum.3Further arguments raged as to whether tricuspid atresia should be included within the univentricular category.4,5The debate is rationalised when we recognise that all the potentially univentricular hearts are treated nowadays by constructing the Fontan circulation,6or one of its variants,7as indeed are some unequivocally biventricular hearts.8Clarification and simplification of the anatomical arrangement in this functionally univentricular category, as we will show in this review, is provided by rigorous application of the crucial philosophic principle of analysis called the “Morphological Method”,9coupled with separate analysis of the ventricular mass and the atrioventricular junctions.10,11