The first multicentre study on coronary anomalies in the Netherlands: MuSCAT.

BACKGROUND: Current guidelines on coronary anomalies are primarily based on expert consensus and a limited number of trials. A gold standard for diagnosis and a consensus on the treatment strategy in this patient group are lacking, especially for patients with an anomalous origin of a coronary artery from the opposite sinus of Valsalva (ACAOS) with an interarterial course. AIM: To provide evidence-substantiated recommendations for diagnostic work-up, treatment and follow-up of patients with anomalous coronary arteries. METHODS: A clinical care pathway for patients with ACAOS was established by six Dutch centres. Prospectively included patients undergo work-up according to protocol using computed tomography (CT) angiography, ischaemia detection, echocardiography and coronary angiography with intracoronary measurements to assess anatomical and physiological characteristics of the ACAOS. Surgical and functional follow-up results are evaluated by CT angiography, ischaemia detection and a quality-of-life questionnaire. Patient inclusion for the first multicentre study on coronary anomalies in the Netherlands started in 2020 and will continue for at least 3 years with a minimum of 2 years of follow-up. For patients with a right or left coronary artery originating from the pulmonary artery and coronary arteriovenous fistulas a registry is maintained. RESULTS: Primary outcomes are: (cardiac) death, myocardial ischaemia attributable to the ACAOS, re-intervention after surgery and intervention after initially conservative treatment. The influence of work-up examinations on treatment choice is also evaluated. CONCLUSIONS: Structural evidence for the appropriate management of patients with coronary anomalies, especially (interarterial) ACAOS, is lacking. By means of a structured care pathway in a multicentre setting, we aim to provide an evidence-based strategy for the diagnostic evaluation and treatment of this patient group.

Lack of diagnostic utility of the ECG-derived ventricular gradient in patients with suspected acute pulmonary embolism.

INTRODUCTION: The YEARS algorithm was successfully developed to reduce the number of computed tomography pulmonary angiography (CTPA) investigations in the diagnostic management of patients with suspected pulmonary embolism (PE), although half of patients still needed to be referred for CTPA. We hypothesized that ECG derived ventricular gradient optimized for right ventricular pressure overload (VG-RVPO), an easy to use tool for detecting PE-induced pulmonary hypertension (PH), may further improve the efficiency of the YEARS algorithm. METHODS: In this post-hoc analysis of the Years study, ECGs of 479 patients with suspected PE managed according to the YEARS algorithm were available for analysis. The diagnostic performance of VG-RVPO was assessed and likelihood ratios were calculated. RESULTS: PE was diagnosed in 88 patients (18%). In patients with confirmed PE, 34% had an abnormal VG-RVPO versus 24% of those without PE (odds ratio 1.6; 95%CI 0.94-2.6). The mean VG-RVPO was -22 ± 13 and did not differ between the two patient groups (-22 versus -20; mean difference - 2, 95% CI -4.8 to 1.3). The sensitivity of VG-RVPO for PE was 24% (95%CI 34-45), the specificity 76% (95%CI 71-80) and the c-statistic 0.45 (95% CI 0.38-0.51). When combined with the YEARS algorithm, the likelihood ratios of VG-RVPO remained close to 1.0. Ruling out PE in patients with an indication for CTPA based on a normal VG-RVPO would have resulted in 58 missed cases. CONCLUSIONS: The VG-RVPO has no diagnostic value for suspected acute PE, either as stand-alone diagnostic test or combined with the YEARS algorithm. CONDENSED ABSTRACT: This post-hoc analysis of the YEARS study failed to demonstrate incremental diagnostic value of VG-RVPO for acute PE, either as stand-alone diagnostic test or combined with the YEARS algorithm. Nevertheless, the role of VG-RVPO recorded on admission could potentially be valuable in the risk stratification of PE during hospitalization, although this remains to be studied.

Prognostic Importance of Increased Right Ventricular Afterload in Orthotopic Liver Transplantation Recipients With Endstage Cirrhosis.

BACKGROUND: Severely increased right ventricular (RV) afterload is considered a contra-indication for orthotopic liver transplantation (OLT). This study assesses the effects of mildly increased RV afterload on long-term outcome after OLT in relation to RV function. METHODS: 139 OLT recipients (53±12years, 76% male) were included. Preoperative RV afterload was assessed invasively or, if not available, echocardiographically and categorised as normal, high-normal (mean pulmonary artery pressure [PAP] 20-25mmHg or echocardiographic systolic PAP 35-40mmHg) or mildly elevated (mean PAP 25-35mmHg or systolic PAP 40-50mmHg). The association between level of RV afterload, echocardiographic RV function and postoperative outcome was assessed. RESULTS: Right ventricular afterload was high-normal in 17% and mildly elevated in 12% of patients. Patients with elevated RV afterload had higher echocardiographic RV dimensions and left ventricular filling pressures. RV functional parameters were within normal range and not associated with RV afterload. Increased RV afterload was associated with a higher incidence of postoperative haemodynamic complications (8%, 17%, and 29% for normal, high-normal and mildly elevated RV afterload, respectively, p=0.03) and worse survival (8-year survival 74%, 41% and 37% respectively, p=0.01). Preoperative RV function was not associated with outcome after OLT. CONCLUSIONS: Increased RV afterload was associated with increased haemodynamic complications and worse long-term survival in OLT recipients. Right ventricular function in patients with increased RV afterload was within normal range and not associated with postoperative outcome.

Ventricular assist device implantation in patients with a failing systemic right ventricle: a call to expand current practice.

Ventricular assist device (VAD) implantation is an established treatment modality for patients with end-stage heart failure, and improves symptoms and survival. In the Netherlands, it is not yet routinely considered in patients with congenital heart disease and failing systemic right ventricle (SRV). Recently, a VAD was implanted in 2 SRV patients, one who underwent a Mustard procedure during infancy for transposition of the great arteries (male, 47 years old) and one with a congenitally corrected transposition of the great arteries (male, 54 years old). The first patient is doing well >1 year after implantation; the second patient will be discharged home soon. These examples and other reports demonstrate the feasibility of adopting VAD implantation into routine care for SRV failure. In conclusion, patients with SRV failure may be suitable candidates for VAD implantation: they are relatively young, usually have a preserved subpulmonary left ventricular function, and their specific anatomical and physiological characteristics often make them unsuitable for cardiac transplantation. Therefore it is important to recognise the possibility of VAD implantation early in the process of SRV failure, and to timely refer these patients to a heart failure clinic with experience in VAD implantation in this group of patients for optimisation, screening, and implantation.

Electrocardiographic detection of pulmonary hypertension in patients with systemic sclerosis using the ventricular gradient.

BACKGROUND: Pulmonary hypertension (PH) is a leading cause of death in systemic sclerosis (SSc) patients. The current study assessed the ability of the ECG-derived ventricular gradient (VG-RVPO) to detect PH and predict all-cause mortality in PH patients with subtypes of SSc differing in the extent of multi-organ involvement. METHODS: ECGs were obtained from 196 patients with limited and 77 patients with diffuse SSc included from our screening programme on cardiac complications. The association of the VG-RVPO with (1) the presence of PH, (2) conventional screening parameters and (3) survival in PH patients was assessed. RESULTS: In limited SSc patients an elevated VG-RVPO corresponded with the presence of PH (-5±12 mV.ms vs -22±16 mV.ms, P<0.01), correlated significantly with conventional screening parameters and had a better diagnostic performance than the presence of a right heart axis (AUC 0.81 vs 0.60; P=0.04). These differences were not observed in patients with diffuse SSc. An elevated VG-RVPO was associated with decreased survival in all SSc patients with PH (3 year survival 30% vs 64%, P=0.02). CONCLUSION: An elevated VG-RVPO is associated with PH in limited SSc patients and with decreased survival in all SSc patients with PH.

Tailored circulatory intervention in adults with pulmonary hypertension due to congenital heart disease.

BACKGROUND: Adults with pulmonary hypertension associated with congenital heart disease (PH-CHD) often have residual shunts. Invasive interventions aim to optimise pulmonary flow and prevent right ventricular failure. However, eligibility for procedures strongly depends on the adaptation potential of the pulmonary vasculature and right ventricle to resultant circulatory changes. Current guidelines are not sufficiently applicable to individual patients, who exhibit great diversity and complexity in cardiac anomalies. METHODS AND RESULTS: We present four complex adult PH-CHD patients with impaired pulmonary flow, including detailed graphics of the cardiopulmonary circulation. All these patients had an ambiguous indication for shunt intervention. Our local multidisciplinary Grown-Ups with Congenital Heart Disease team reached consensus regarding a patient-tailored invasive treatment strategy, adjacent to relevant guidelines. Interventions improved pulmonary haemodynamics and short-term clinical functioning in all cases. CONCLUSIONS: Individual evaluation of disease characteristics is mandatory for tailored interventional treatment in PH-CHD patients, adjacent to relevant guidelines. Both strict registration of cases and multidisciplinary and multicentre collaboration are essential in the quest for optimal therapy in this patient population.

Myocardial bridging: what have we learned in the past and will new diagnostic modalities provide new insights?

The clinical significance of myocardial bridging has been a subject of discussion and controversy since the introduction of coronary arteriography (CAG) in the early 1960s. More recently computed tomography coronary angiography (CTCA) has made it possible to visualise the overlying muscular bands and appears to have a higher sensitivity for detecting myocardial bridging than CAG. Combining CTCA with invasive techniques such as CAG should make it possible to improve our understanding of the pathophysiology of myocardial bridging and to provide answers to hitherto unresolved questions. This paper critically reviews the outcomes of previous studies and defines remaining questions that should be answered to optimise the management of the presumably fast growing number of patients in whom a diagnosis of myocardial bridging has been made.

Ebstein's anomaly may be caused by mutations in the sarcomere protein gene MYH7.

Ebstein's anomaly is a rare congenital heart malformation characterised by adherence of the septal and posterior leaflets of the tricuspid valve to the underlying myocardium. Associated abnormalities of left ventricular morphology and function including left ventricular noncompaction (LVNC) have been observed. An association between Ebstein's anomaly with LVNC and mutations in the sarcomeric protein gene MYH7, encoding ß-myosin heavy chain, has been shown by recent studies. This might represent a specific subtype of Ebstein's anomaly with a Mendelian inheritance pattern. In this review we discuss the association of MYH7 mutations with Ebstein's anomaly and LVNC and its implications for the clinical care for patients and their family members.

A percutaneous treatment strategy of an adult patient with a bicuspid aortic valve, coarctation of the aorta, and an exceptionally large aneurysm of a collateral artery: Case report and literature overview.

Coarctation of the aorta (CoA) is a congenital heart defect that is associated with a bicuspid aortic valve (BAV), ascending aorta dilatation, intracerebral aneurysms, and premature atherosclerotic disease. The first presentation during late adulthood is rare and is frequently driven by late sequelae. Hypertrophic collateral arteries can develop aneurysms which are at risk for spontaneous rupture, however, treatment recommendations for these aneurysms are scarce. Here, we describe the clinical course and percutaneous treatment strategy of a patient with a late diagnosis of a pin-point CoA, a BAV with moderate regurgitation, and an exceptionally large aneurysm of a collateral artery. A 59-year-old woman was diagnosed with Streptococcus bovis endocarditis of a BAV with moderate aortic valve regurgitation and small vegetation (<5 mm) on the non-coronary cusp. Work-up revealed hypertension and adenocarcinoma in situ of the ascending colon, considered the bacteremia porte d'entrée, for which a curative hemicolectomy was performed. Echocardiography showed a narrowing of the aorta distal from the origin of the left subclavian artery with the antegrade diastolic flow with a pathognomonic "sawtooth" pattern and an estimated pressure gradient of >70 mmHg. Computed tomography angiography (CTA) showed a network of well-developed collateral arteries and a levoatriocardinal vein. One of the collateral arteries arising from the left subclavian artery revealed an exceptionally large aneurysmatic dilation (29 × 24 × 24 mm). The invasive assessment confirmed a hemodynamically significant CoA. Treatment involved balloon dilatation and placement of a covered stent at the site of the pin-point CoA and a percutaneous coronary intervention (PCI) of the stenosis in the left anterior descending artery. No residual gradient over the CoA was observed. Antihypertensive drugs could be discontinued, and CTA performed 4 months later showed regression and thrombosis of the numerous collaterals and, importantly, thrombosis of the large aneurysm. This case illustrates the late diagnosis of CoA with associated congenital heart defects and late sequelae including hypertension, BAV endocarditis, coronary artery disease, and aneurysm formation of the extensive collateral network. The patient underwent pharmacological and percutaneous treatment, ultimately resulting in the alleviation of the CoA, normalization of the blood pressure, reduction of collateral flow, and thrombosis of the large aneurysm of the collateral artery.

The aortic root in repaired tetralogy of Fallot: Serial measurements and impact of losartan treatment.

BACKGROUND: Aortic root dilatation is common in adults with repaired tetralogy of Fallot (rTOF) and might lead to aortic dissection. However, little is known on progression of aortic dilatation and the effect of pharmaceutical treatment. This study aims to determine factors associated with aortic growth and investigate effects of losartan. METHODS AND RESULTS: We performed a prespecified analysis from the 1:1 randomized, double-blind REDEFINE trial. Aortic root diameters were measured at baseline and after 2.0 ± 0.3 years of follow-up using cardiovascular magnetic resonance (CMR) imaging. A total of 66 patients were included (68% men, age 40 ± 12 years, baseline aortic root 37 ± 6 mm, 32% aortic dilatation (>40 mm)). There was a trend towards slow aortic root growth (+0.6 ± 2.3 mm after two years, p = 0.06) (n = 60). LV stroke volume was the only factor associated with both a larger baseline aortic root (ß: 0.09 mm/ml (95% C.I.:0.02, 0.15), p = 0.010) and with aortic growth during follow-up (ß: 0.04 mm/ml (95% C.I.:0.005, 0.066), p = 0.024), after correction for age, sex, and body surface area using linear regression analysis. No treatment effect of losartan was found (p = 0.17). CONCLUSIONS: Aortic root dilatation was present in about one-third of rTOF patients. A larger LV stroke volume was associated with both a larger baseline aortic root and ongoing growth. Our findings provide no arguments for lower aortic diameter thresholds for prophylactic surgery compared to the general population.

Pregnancy outcome in women with repaired versus unrepaired isolated ventricular septal defect.

OBJECTIVE: To compare the risks of pregnancy complications in women with repaired and unrepaired isolated ventricular septal defect (VSD). DESIGN: A retrospective multicentre study. SETTING: Tertiary centres in the Netherlands and Belgium. METHODS: Women were identified using two congenital heart disease registries. Eighty-eight women were identified who had experienced 202 pregnancies, including 46 miscarriages and nine terminations of pregnancy. Information on each completed pregnancy (n = 147; unrepaired VSD, n = 104; repaired VSD, n = 43) was obtained using medical records and telephone interviews. Data from the Generation R database (prospective cohort study; n = 9667) were used to determine the background risk (controls). Odds ratios and 95% CI were estimated using general estimation equation analysis adjusted for multiple pregnancies per woman, maternal age and parity status. MAIN OUTCOME MEASURES: Adjusted odds ratios (AORs) for developing pregnancy complications in relation to corrective status. RESULTS: Pregnancies in women with an unrepaired VSD were associated with a higher risk of pre-eclampsia (AOR 4.59, 95% CI 2.01-10.5, P < 0.001) compared with controls. No differences were observed when comparing women with repaired VSD and controls. Pregnancies in women with repaired VSD were associated with a higher risk of premature labour (AOR 4.02, 95% CI 1.12-14.4, P = 0.03) and small-for-gestational-age (SGA) births (AOR 4.09, 95% CI 1.27-13.2, P = 0.02) compared with women with unrepaired VSD. CONCLUSIONS: Women with unrepaired VSD are at increased risk of pre-eclampsia, which suggests that it is not a benign condition. In addition, women with repaired VSD are at increased risk of premature labour and SGA births compared with women with unrepaired VSD.

Comparison of pregnancy outcomes in women with repaired versus unrepaired atrial septal defect.

OBJECTIVE: To compare the risks of complications during pregnancy in women with repaired and unrepaired atrial septal defects (ASDs) without associated complex cardiac lesions. DESIGN: A retrospective multicentre study. SETTING: Tertiary centres in the Netherlands and Belgium. POPULATION: Women with ASD without associated complex cardiac lesions. METHODS: Women were identified using two congenital heart disease registries. One hundred women were identified who had 243 pregnancies, including 49 miscarriages and six terminations of pregnancy. Detailed information on each completed pregnancy (n = 188; unrepaired ASD, n = 133; repaired ASD, n = 55) was obtained using medical records and telephone interviews. In addition, data from the Generation R database (a prospective cohort study; n = 9667) were used to determine the background risk (control group). MAIN OUTCOME MEASURES: Adjusted odds ratios (AORs) for cardiac, obstetric and neonatal events controlled for multiple pregnancies per woman using general estimating equation analysis. RESULTS: Women with an unrepaired ASD had a higher risk of neonatal events (AOR = 2.99, 95% confidence interval [CI] 1.14-7.89, P = 0.027) than women with a repaired ASD. The risk of cardiac and obstetric complications was comparable between women with unrepaired and repaired ASDs. Compared with the general population, women with an unrepaired ASD had higher risks of pre-eclampsia (AOR = 3.54, 95% CI 1.26-9.98, P = 0.017), small-for-gestational-age births (AOR = 1.95, 95% CI 1.15-3.30, P = 0.013) and fetal mortality (AOR = 5.55, 95% CI 1.77-17.4, P = 0.003). By contrast, no differences were observed when comparing women with a repaired ASD versus controls. CONCLUSIONS: Women with an unrepaired ASD are at increased risk of neonatal events in comparison with women with a repaired ASD. Compared with the general population, women with an unrepaired ASD are at increased risk of pre-eclampsia, small-for-gestational-age births and fetal mortality.

Pulmonary hypertension: the role of the electrocardiogram.

A 54-year-old female was referred to our centre for further evaluation of recently established severe pulmonary hypertension. Six months prior to presentation to the cardiologist of the referring centre, the patient had first experienced exertional dyspnoea. At the time of presentation to the referring cardiologist, the patient's ECG showed signs of an increased right heart load. Interestingly, this patient had undergone a thorough cardiac evaluation in the referring centre seven years before when she presented with severe hyperthyroidism. At that time there were no symptoms or signs of pulmonary hypertension on ECG, echocardiography, or at heart catheterisation. Thorough evaluation in cooperation with the referring centre demonstrated that this patient was suffering from idiopathic pulmonary arterial hypertension, a rare form of pulmonary hypertension. We conclude this report with a discussion on the potential use of the ECG for the diagnosis of increased right heart load. (Neth Heart J 2008;16:250-4.).

ECG derived ventricular gradient exceeds echocardiography in the early detection of pulmonary hypertension in scleroderma patients.

BACKGROUND: Patients with systemic sclerosis (SSc) are at risk for developing pulmonary hypertension (PH) which is a major cause of death in this population. Echocardiographic (TTE) derived pulmonary arterial pressure (PAP) can be unreliable for the early detection of PH. Previous studies demonstrate that the ECG derived ventricular gradient optimized for right ventricular pressure overload (VG-RVPO) can detect PH in a heterogeneous population suspected of PH. The aim of this study is to assess the use of the VG-RVPO as a screening and monitoring instrument of early PH in SSc patients. METHODS: Serial ECGs and TTEs from twenty-seven SSc patients who underwent right heart catheterization (RHC) were retrospectively analyzed. The changes in PAP and VG-RVPO over time were studied in patients with and without diagnosed PH. RESULTS: Twenty-four patients (52.5% female, mean age 58.4 years SD 14.3) were studied. In eleven patients PH was confirmed with RHC. In these patients VG-RVPO was significantly higher -8 ±â€¯19 than in patients without PH -23 ±â€¯10 mV·ms, (P < 0.05). In addition, in PH patients the VG-RVPO increased over time in contrast to patients without PH (P < 0.01). The VG was more sensitive to detect disease progression in earlier stages of disease as compared to echocardiographic derived PAP. CONCLUSIONS: The VG-RVPO is a sensitive, non-invasive and cost effective tool for early detection of PH in SSc patients. Serial measurements indicate that the VG-RVPO can be used as a follow-up instrument and outperforms TTE to detect early changes in right ventricular pressure over time.

Clinical course of tricuspid regurgitation in repaired tetralogy of Fallot.

BACKGROUND: Little is known on the clinical course of tricuspid regurgitation (TR) in patients with repaired tetralogy of Fallot (rTOF) and which patients are at particular risk. This study aims to determine TR course, characteristics associated with TR progression, and the prognostic relevance of TR in rTOF patients. METHODS: In this dualcenter cohort study, rTOF patients from a prospective national registry with ≥1 cardiac magnetic resonance imaging study and ≥2 echocardiograms available were included. Clinical and imaging data were collected. Cox hazards regression analysis was used to assess patient characteristics associated with progression to severe TR and whether severe TR was associated with the combined clinical endpoint of tachyarrhythmia, heart failure, and death, as time-dependent factor. RESULTS: A total of 216 patients were included (57% men, age 34±12years); 11 patients (5%) had severe TR at baseline. During 7.6±3.5years of follow-up, progression to severe TR occurred in 15 patients (7%). NYHA class ≥2 (HR 5.38, 95%-C.I. 1.91-15.16, p=0.001) and moderate baseline TR (HR 13.10, 95%-C.I. 2.95-58.21, p=0.001) were independently associated with progression to severe TR. Adverse events occurred in 47 patients (22%). The occurrence of severe TR was independently associated with adverse events (HR 3.48, 95%-C.I. 1.68-7.21, p=0.001). CONCLUSIONS: In this study, severe TR was present in 12% of adult rTOF patients during 7.6years, and progression to severe TR was most likely in symptomatic patients with moderate baseline TR. In these patients, close surveillance is warranted, because the occurrence of severe TR was associated with worse prognosis.

Derivation of a clinical prediction score for chronic thromboembolic pulmonary hypertension after acute pulmonary embolism.

UNLABELLED: Essentials Predicting chronic thromboembolic pulmonary hypertension (CTEPH) after pulmonary embolism is hard. We studied 772 patients with pulmonary embolism who were followed for CTEPH (incidence 2.8%). Logistic regression analysis revealed 7 easily collectable clinical variables that combined predict CTEPH. Our score identifies patients at low (0.38%) or higher (10%) risk of CTEPH. SUMMARY: Introduction Validated risk factors for the diagnosis of chronic thromboembolic pulmonary hypertension (CTEPH) after acute pulmonary embolism (PE) are currently lacking. Methods This is a post hoc patient-level analysis of three large prospective cohorts with a total of 772 consecutive patients with acute PE, without major cardiopulmonary or malignant comorbidities. All underwent echocardiography after a median of 1.5 years. In cases with signs of pulmonary hypertension, additional diagnostic tests to confirm CTEPH were performed. Baseline demographics and clinical characteristics of the acute PE event were included in a multivariable regression analysis. Independent predictors were combined in a clinical prediction score. Results CTEPH was confirmed in 22 patients (2.8%) by right heart catheterization. Unprovoked PE, known hypothyroidism, symptom onset > 2 weeks before PE diagnosis, right ventricular dysfunction on computed tomography or echocardiography, known diabetes mellitus and thrombolytic therapy or embolectomy were independently associated with a CTEPH diagnosis during follow-up. The area under the receiver operating charateristic curve (AUC) of the prediction score including those six variables was 0.89 (95% confidence interval [CI] 0.84-0.94). Sensitivity analysis and bootstrap internal validation confirmed this AUC. Seventy-three per cent of patients were in the low-risk category (CTEPH incidence of 0.38%, 95% CI 0-1.5%) and 27% were in the high-risk category (CTEPH incidence of 10%, 95% CI 6.5-15%). Conclusion The 'CTEPH prediction score' allows for the identification of PE patients with a high risk of CTEPH diagnosis after PE. If externally validated, the score may guide targeting of CTEPH screening to at-risk patients.

Relation between ventricular DNA content and number of myocytes and non-myocytes in hearts of normotensive and spontaneously hypertensive rats.

Myocardial DNA concentration and ventricular weight were measured in the hearts of normal and spontaneously hypertensive rats varying in age from 1 day to 1 year and the ventricular DNA content calculated. A linear relation between ventricular DNA content and ventricular weight was observed in both rat strains. This linear relation was deduced theoretically, assuming that the number of ventricular non-myocytes per heart was proportional to ventricular weight and that the number of ventricular myocytes per heart was constant after the first postnatal week. The fit with experimental data produced values of the number of ventricular myocytes (42.5 X 10(6] and non-myocytes (199 X 10(6) per gram of ventricular tissue) in normal rat heart. Using published data on ventricular volume occupied by myocytes (80%) and myocardial specific density (1.06 g X ml-1), the mean(SD) volume of individual myocytes could be calculated (17758(2632) multiplied by ventricular weight, expressed in micron 3 X g). The values obtained compared well with experimental observations reported in the present study (18504(131) micron 3 X g) and in other studies. Hearts from spontaneously hypertensive rats had lower numbers of myocytes (37.4 X 10(6] and non-myocytes (180 X 10(6) per gram) per heart than normal hearts with identical ventricular weights. Hearts of normal 2 month old rats that were made hypertrophic by various means were identical to non-hypertrophic hearts of normal older rats with identical ventricular weights in relation to the number of ventricular myocytes and non-myocytes per heart. It is concluded that ventricular hypertrophy induced in young adult rats might be regarded as normal growth occurring at an accelerated rate.

Comparison of myocardial changes between pressure induced hypertrophy and normal growth in the rat heart.

To evaluate differences in tissue composition between hearts with pressure overload hypertrophy and normal hearts of comparable weight, 30 rat hearts with aortic constriction of 4, 10 and 30 days, and nine hearts of sham operated controls were studied. Surgery was performed at age 70 days. Morphometric analysis of myocardial tissue sections revealed (1) myocyte hypertrophy in left ventricular myocardium of hypertrophic hearts was proportional to heart weight, and in normal growth myocyte volume increased in proportion to heart weight; (2) myocyte number in left ventricular myocardium was identical in hypertrophic and normal hearts; (3) non-muscle cell proliferation was proportional to heart weight identically in hypertrophic and normal hearts; (4) volume fractions of myocytes were significantly lower in hypertrophic hearts [0.76(SD 0.05)] than in normal hearts [0.82(0.04)]; (5) volume fractions of all nuclei, myocyte nuclei and non-myocyte nuclei were similar in hypertrophic and normal hearts; (6) measured ventricular DNA content increased with heart weight identically in hypertrophic and normal hearts, and equalled DNA content calculated using the data on tissue composition. Neither right ventricular weight nor right ventricular DNA content were affected by the presence of left ventricular hypertrophy. We conclude that left ventricular hypertrophy due to aortic constriction in the rat resulted in changes of myocardial tissue composition similar to the changes associated with normal growth. Tissue composition of hypertrophic rat hearts corresponds strikingly to that of normal rat hearts with comparable heart weight, although myocardial changes in hypertrophy develop considerably faster than in normal growth.

Morphometric quantification of myocyte dimensions validated in normal growing rat hearts and applied to hypertrophic human hearts.

To obtain quantitative information on changes in myocyte size in hearts with increased myocardial mass light microscopical morphometry was used in fixed and stained myocardial tissue sections. A modification of the azan staining procedure made longitudinal (sarcolemma) and transverse (intercalated discs) boundaries visible with a contrast that allowed morphometric analysis. The method was validated in left ventricular tissue of rats ranging in age from 4 to 17 weeks. Myocyte width, cut surface area, length, and volume were significantly correlated with left ventricular weight with residual errors of 5%, 5%, 6%, and 8% respectively. The method was applied to 21 human hearts, nine of which had left ventricular hypertrophy. Myocyte width, area, length, and volume both in subepicardial and subendocardial left ventricular tissue were significantly greater in hypertrophic than in normal hearts. Although the mean weight of the hypertrophic hearts exceeded that of normal hearts by 40%, myocyte volumes in subepicardial and subendocardial left ventricular tissue of hypertrophic hearts were higher by 78% and 43% respectively, indicating a transmural difference in the extent of myocyte hypertrophy. The method is accurate and reproducible and gives useful quantitative information on changes in myocyte dimensions during normal cardiac growth as well as in cardiac hypertrophy.