The relationship between magnesium and ambulatory blood pressure,augmentation index,pulse wave velocity,total peripheral resistance,and cardiac output in essential hypertensive patients

Magnesium levels have been shown to be associated with elevated blood pressure (BP), endothelial dysfunction, insulin resistance, vascular calcification, inflammation, and atherosclerosis. It was also demonstrated that patients with hypertension have increased inflammation, insulin resistance, and endothelial dysfunction. However, the relationship between magnesium, ambulatory BPs, and central hemodynamic parameters were not evaluated extensively. Serum magnesium levels, ambulatory blood pressures, augmentation index (Aix), pulse wave velocity, total peripheral resistances, and cardiac output were measured for all patients. In total, 184 essential hypertension patients were enrolled. In univariate analysis, magnesium levels were correlated with hemoglobin (r = +0.155; P = .037), albumin (r = +0.180; P = .018), pulse pressure (daytime; r = −0.170; P = .021), pulse pressure (24-hour; r = −0.156; P = .035), Aix (daytime; r = −0.223; P = .002), Aix (nighttime; r = −0.169; P = .022), and Aix (24-hour; r = −0.247; P = .001). In regression analysis, magnesium levels were independently and conversely associated with daytime Aix (P < .0001), nighttime Aix (P = .019), and 24-hour Aix (P < .0001). We suggest that magnesium levels were associated with Aix but not with total peripheral resistances, pulse wave velocity, cardiac output, and central BPs. The unique mechanisms related with magnesium and Aix but not shared by other central parameters needs to be determined.     

Effect of isosorbide dinitrate on cardiac output in severe cardiac failure: relation to initial hemodynamics, ventricular volume, and the preload reserve mechanism

Isosorbide dinitrate (ISDN) improves the clinical and hemodynamic state of patients with heart failure, but may cause dizziness and syncope. To characterize patients in whom cardiac output falls with high-dose nitrate therapy and to examine further the pathophysiology of the fall in cardiac output in these patients, we studies the effect of sublingual ISDN on forward cardiac output in 14 patients with severe cardiac failure (New York Heart Association grades 3-4). We examined systolic and diastolic left ventricular (LV) function from pressure and volume analyses of LV function. After administration of 15 mg ISDN, cardiac output was either unaltered or increased in 7 patients (Group 1) (11 +/- 12%, mean +/- SD), and decreased in 7 (Group 2) (-13 +/- 10%) (Group 1 vs. 2, p less than 0.002). Initial systemic arterial pressure, LV ejection fraction, wedge and LV transmural filling pressures were similar in both groups, but Group 2 patients had a lower systemic vascular resistance (p = 0.07) and tended to have a larger initial LV end-diastolic volume and increased end-diastolic compliance; following ISDN the decrease in LV filling pressure and end-diastolic volume was larger and the product of the changes greater (p less than 0.02). Thus ISDN decreases filling pressure and improves forward cardiac output in some patients with congestive heart failure, but large doses may decrease cardiac output in a subset of patients who have a lower systemic vascular resistance and a larger more compliant ventricle, maintaining forward blood flow predominantly by a preload reserve mechanism.(ABSTRACT TRUNCATED AT 250 WORDS)     

Measurement of volumetric mitral and aortic blood flow based on a new freehand three-dimensional colour flow imaging method. An in vivo validation.

AIMS: To validate a new three-dimensional (3D) colour flow method used to calculate cardiac output (CO) in aortic and mitral blood flow. METHODS: The transducer was freely tilted transthoracically using a magnetic locating device recording its spatial position. Raw digital ultrasound data were recorded in healthy subjects during 10-20 heartbeats at a high frame rate ranging from 41 to 66 frames/s and analysed off-line with no loss in temporal resolution. Blood flow velocities aligned with the ultrasound beam were integrated across a moving spherical surface to calculate volumetric flow. RESULTS: The range of agreement between the 3D mitral and 3D aortic method was 0.04+/-1.32 l/min (mean+/-2 standard deviations). The range of agreement between 3D aortic flow and the two-dimensional (2D) pulsed wave Doppler method (2DPW) in the left ventricular outflow tract (LVOT) was 0.7+/-1.7 l/min, while the range of agreement between 3D mitral flow and the 2DPW method was 0.88+/-1.64 l/min. CONCLUSION: The 3D methods agreed well. The 3D volumetric flow overestimated the 2DPW method, as expected, and the range of agreement was wide. The common pitfalls in pulsed wave ultrasound methods to calculate CO were avoided, as the 3D method was angle-independent, no assumptions about the velocity profile were made, and a moving sample surface was applied. The acquisition of data was fast and easy and high temporal resolution was achieved.     

Estimation of cardiac reserve by peak power: validation and initial application of a simplified index

OBJECTIVES—To validate a simplified estimate of peak power (SPP) against true (invasively measured) peak instantaneous power (TPP), to assess the feasibility of measuring SPP during exercise and to correlate this with functional capacity.
DESIGN—Development of a simplified method of measurement and observational study.
SETTING—Tertiary referral centre for cardiothoracic disease.
SUBJECTS—For validation of SPP with TPP, seven normal dogs and four dogs with dilated cardiomyopathy were studied. To assess feasibility and clinical significance in humans, 40 subjects were studied (26 patients; 14 normal controls).
METHODS—In the animal validation study, TPP was derived from ascending aortic pressure and flow probe, and from Doppler measurements of flow. SPP, calculated using the different flow measures, was compared with peak instantaneous power under different loading conditions. For the assessment in humans, SPP was measured at rest and during maximum exercise. Peak aortic flow was measured with transthoracic continuous wave Doppler, and systolic and diastolic blood pressures were derived from brachial sphygmomanometry. The difference between exercise and rest simplified peak power (Δ SPP) was compared with maximum oxygen uptake (O₂max), measured from expired gas analysis.
RESULTS—SPP estimates using peak flow measures correlated well with true peak instantaneous power (r = 0.89 to 0.97), despite marked changes in systemic pressure and flow induced by manipulation of loading conditions. In the human study, O₂max correlated with Δ SPP (r = 0.78) better than Δ ejection fraction (r = 0.18) and Δ rate-pressure product (r = 0.59).
CONCLUSIONS—The simple product of mean arterial pressure and peak aortic flow (simplified peak power, SPP) correlates with peak instantaneous power over a range of loading conditions in dogs. In humans, it can be estimated during exercise echocardiography, and correlates with maximum oxygen uptake better than ejection fraction or rate-pressure product.


Keywords: stress echocardiography; oxygen consumption; left ventricular function; cardiac power output     

Beneficial effects of exercise training in heart failure patients with low cardiac output response to exercise – a comparison of two training models

BACKGROUND: Exercise capacity of patients with chronic heart failure (CHF) correlates poorly with estimates of cardiac function. Yet, it has been suggested that only patients without severely impaired cardiac output (CO) benefit from exercise training. Comparisons of different training models have not been made in the same study. AIMS: To evaluate whether the response to different training models diverges according to the cardiac output response to exercise in patients with chronic heart failure. METHODS: Sixteen CHF patients (63 +/- 11 years) with an ejection fraction of 30 +/- 11% underwent a baseline cardiopulmonary exercise test, right heart catheterization and leg muscle biopsy. Cardiac output (CO) response to exercise was defined as the ratio between CO increase and the increase in oxygen uptake (CO response index) during exercise. Patients were randomized into two training regimens, differing with regard to active muscle mass, i.e. whole body and one-legged exercise. RESULTS: Baseline exercise capacity expressed as W kg-1 correlated with the CO response index (r = 0.51, P < 0.05). Exercise capacity on the cycle ergometer increased in both groups but more in the one-legged than in the two-legged training group (P < 0.05). The improvement in exercise capacity did not correlate with base-line exercise capacity. It correlated with CO response index in the one-legged (r = 0.75, P < 0.01) but not in the two-legged training group. CO response index correlated negatively with the pulmonary capillary wedge pressure at peak exercise (r = - 0.60, P < 0.05). The increase in leg muscle citrate synthase activity after training correlated negatively with the baseline CO response index (r = - 0. 50, P < 0.05). CONCLUSIONS: The improvement of exercise capacity after one-legged training correlates with the CO increase in relation to the O2 uptake before training. In patients with low CO response, individualization of the exercise regimen is needed and the benefits of training a limited muscle mass at a time deserve further study.     

Physiological cardiac reserve: development of a non-invasive method and first estimates in man

Objective—To investigate whether physiological cardiac reserve can be measured in man without invasive procedures and whether it is a major determinant of exercise capacity.
Design—Development of method of measurement and an observational study.
Setting—A regional cardiothoracic centre.
Subjects—70 subjects with a wide range of cardiac function, from heart failure patients to athletes.
Methods—Subjects underwent treadmill, symptom limited cardiopulmonary exercise tests to measure aerobic exercise capacity (represented by O₂max) and cardiac reserve. Cardiac output was measured non-invasively using the CO₂ rebreathing technique.
Results—Cardiac power output (CPO_max) at peak exercise was found to be significantly related to aerobic capacity: CPO_max (W) = 0.35 + 1.5O₂max (l/min), r = 0.87, p < 0.001. It also correlated well with exercise duration (r = 0.62, p < 0.001), suggesting that cardiac reserve is a major determinant of exercise capacity. In the study, cardiac reserve ranged from 0.27 to 5.65 W, indicating a 20-fold difference between the most impaired cardiac function and that of the fittest subject.
Conclusions—A non-invasive method of estimating physiological cardiac reserve was developed. The reserve was found to be a major determinant of exercise capacity in a population of normal subjects and patients with heart disease. This method may thus be used to provide a clearer definition of the extent of cardiac impairment in patients with heart failure.

Keywords: cardiac reserve;  cardiac power output;  oxygen consumption;  congestive heart failure     

Development and validation of a nomogram model for early postoperative hyperlactatemia in patients undergoing cardiac surgery

BackgroundPostoperative hyperlactatemia (POHL) is common in patients undergoing cardiac surgery, associated with adverse outcomes. The aim of this study was to identify predictors for POHL after cardiac surgery and to develop and validate a predictive model.MethodsAdult patients who underwent open heart surgery at our institution between 2016 and 2019 were retrospectively included. The patients were randomly divided into training and validation groups at a 2:1 ratio. Multivariate logistic regression was performed to identify independent predictors for POHL in the training set. A nomogram was then constructed and was validated in the validation set.ResultsPOHL developed in 713 of the 5,323 patients (13.4%). The mortality rate was higher in patients with POHL compared with patients without that (9.5% vs. 2.1%, P<0.001). Age, white blood cell (WBC) count, left ventricular ejection fraction, renal insufficiency, cardiac surgery history, red blood cell (RBC) transfusion, and cardiopulmonary bypass (CPB) time were identified as independent risk factors. The nomogram based on these predictors indicated good discrimination in both the training (c-index: 0.787) and validation (c-index: 0.820) sets. The calibration was reasonable by both visual inspection and goodness-of-fit test. The decision and clinical impact curves demonstrated good clinical utility.ConclusionsWe identified 7 independent risk factors and derived a prediction model for POHL in patients undergoing cardiac surgery. The model may contribute significantly to early risk assessment and clinical intervention.     

Chrome congestive heart failure: Non-invasive measurement of cardiac output by a carbon dioxide rebreathing method at rest and during exercise

Cardiac output was measured in 11 patients undergoing routinecardiac catheterization using a carbon dioxide rebreathing techniqueand compared with cardiac output measured by direct Fick andthermodilution. The carbon dioxide rebreathing technique gaveconsistently lower values for cardiac output than the othertwo methods (mean difference –0·73, 95% CI –0·95to–0·511. min^–1 with the direct Fick and–0·72. 95% CI –1·19 to –0·261.min^–1 with thermodilution). The direct Fick and thermodilutionmethods gave similar results (mean dtfference –0·08,95% CI –0·32 to 0·16a. min^–1). Cardiacoutput was also measured in 10 healthy subjects at rest andduring two steady-state levels of exercise using the carbondioxide rebreathing technique. Measurements were made in triplicateon 3 separate days. The technique gave reproducible resultsbetween replicates at rest (coefficient of variation 91%) andbecame more reproducible on exercise (coefficients of variation56% and 54% respectively at each exercise level). There wasa good correlation between cardiac output and oxygen consumption(r=0·98 The carbon dioxide rebreathing technique is afeasible non-invasive way of measuring cardiac output. It tendsto underestimate cardiac output at rest but is reproducibleand becomes more so on exercise which is where it should beof most value.     

Assessment of left ventricular mechanical dyssynchrony using real time three-dimensional echocardiography: a comparative study to Doppler tissue imaging

Purpose: To assess left ventricular mechanical dyssynchrony (LVMD) using real time three‐dimensional echocardiography (RT3DE) and comparing it with the different dyssynchrony indices derived from Doppler tissue imaging (DTI) for the same patient. Methods: The study included 60 consecutive patients who were considered candidates for CRT, i.e., having ejection fraction ≤35%, NYHA class III or ambulatory class IV, QRS duration ≥120 msec, on optimal pharmacological therapy. Apical RT3DE full volumes were obtained and analyzed to generate the systolic dyssynchrony index (SDI‐16), which is the standard deviation of the time to minimal systolic volume of the 16 segments of LV. Color‐coded DTI was performed for the three standard apical views with estimation of the mechanical dyssynchrony index (12 Ts‐SD), which is the standard deviation of the time to peak systolic velocity at 12 segments of LV. Results: SDI‐16 was 10.96 ± 3.9% (cutoff value: 8.3%), while Ts‐SD was 38 ± 10.2 msec (cutoff value: 32.6 msec). The concordance rate for both indices was 75%; however, there was no correlation between both indices (r = 0.14, P = 0.3). SDI‐16 showed good correlation with QRS duration (r = 0.45, P < 0.001) and inverse correlation with left ventricular ejection fraction (LVEF) calculated by RT3DE (r =?0.37, P = 0.004), while 12 Ts‐SD index showed no correlation with QRS duration (r =?0.0082, P = 0.51) or 2D LVEF (r =?0.26, P = 0.84). Conclusions: RT3DE can quantify LVMD by providing the SDI‐16 and it may prove to be more useful than DTI as it shows increasing dyssynchrony with increased QRS duration and decreased LVEF. (Echocardiography 2012;29:173‐181)     

Damping index of Doppler hepatic vein waveform to assess the severity of portal hypertension and response to propranolol in liver cirrhosis: a prospective nonrandomized study.

BACKGROUND AND AIMS: Alterations in the Doppler hepatic vein (HV) waveform are associated with cirrhosis and portal hypertension. We prospectively evaluated the correlation between the extent of abnormal Doppler HV waveforms expressed as damping index (DI) and the hepatic venous pressure gradient (HVPG) and response to propranolol in patients with cirrhosis. MATERIAL AND METHODS: In 76 patients with cirrhosis (69 men and seven women), both DI of Doppler HV waveform and HVPG were measured, and the relationship between them was analysed. DI was calculated by the minimum velocity/maximum velocity of the HV waveform. An HVPG>12 mmHg was defined as severe portal hypertension. In a subgroup of 19 patients receiving propranolol, changes in both DI and HVPG were evaluated after propranolol administration for 3 months. One author (S. K. B.) performed all DI of Doppler HV waveform studies. RESULTS: Abnormal HV waveforms were seen in 66 of 76 patients (86.8%). DI significantly correlated with the grade of HVPG, i.e. with higher HVPG increased DI was observed (P<0.01). By logistic regression analysis, DI>0.6 was significantly more likely to be severe portal hypertension (odds ratio: 14.19, 95% confidence interval: 4.07-49.55). Receiver-operating characteristic curve according to the value of 0.6 of DI showed a sensitivity of 75.9% and a specificity of 81.8% for the presence of severe portal hypertension. In 19 patients of the propranolol subgroup, change of DI following propranolol treatment also significantly correlated with that of HVPG (P<0.01). CONCLUSIONS: Damping index of the HV waveform by Doppler ultrasonography might be a non-invasive supplementary tool in evaluating the severity of portal hypertension and in responding to propranolol in patients with liver cirrhosis.     

A display of combined left ventricular function and dyssynchrony using Doppler tissue imaging: its application in acute response to cardiac resynchronization therapy

Background: We have recently proposed a novel method for displaying left ventricular (LV) function and mechanical dyssynchrony, which is based on the “vector analysis” using Doppler tissue imaging (DTI). The aim of this study was to examine acute‐phase impact of cardiac resynchronization therapy (CRT) on the parameters assessed by this method. Methods: We studied a total of 25 patients with systolic heart failure, 14 undergoing simultaneous acute pacing‐hemodynamic study and DTI; and 11 patients DTI within a few days before and one week after CRT. Parameters derived from the displaying method were followings: (1) percentage area of the hexagon, the area divided by the overall graph area, reflecting global LV systolic function; (2) net‐delay magnitude, the length of the composite vector for the six vectors, a dyssynchrony index; and (3) delayed contraction site, graphical position of the composite vector. Results: CRT significantly increased cardiac output (3.1 ± 1.0 to 3.4 ± 0.7 L/min, P = 0.02) and +dp/dt (782 ± 149 to 1,089 ± 270 mm Hg/s, P < 0.01), and decreased mitral regurgitaion jet area (7.9 ± 3.0 to 4.8 ± 2.4 cm², P < 0.01). As with the new method, there were significant decreases in the percentage area of the hexagon (20.7 ± 6.6 to 18.6 ± 6.5%, P < 0.01) and the net‐delay magnitude (122 ± 59 to 72 ± 48 ms, P < 0.01). The reduction of net‐delay magnitude accompanied alteration of delayed contraction site; 16 patients had the most delayed site between the lateral and inferior segments before CRT, and seven patients after CRT (P = 0.02). Conclusions: The new method would be a useful tool to assess efficacy of CRT in patients with systolic heart failure. (Echocardiography 2011;28:870‐876)     

Echo determinants of dyssynchrony (atrioventricular and inter- and intraventricular) and predictors of response to cardiac resynchronization therapy

Cardiac resynchronization therapy (CRT) has revolutionized not only the treatment of chronic heart failure but also how we assess left ventricular (LV) dysfunction on echo. Increasingly, it has become clear that identifying and quantifying delays in events during the cardiac cycle is an important assessment in LV dysfunction as it has prognostic implications for patients undergoing CRT. The delays in atrioventricular, right-to-left ventricular, and LV segmental contraction have been shown to be important components in cardiac performance, and this review provides an overview of the commonest methods used for these assessments and their implications for selecting patients for biventricular pacing.     

Accurate method to estimate insulin resistance from multiple regression models using data of metabolic syndrome and oral glucose tolerance test

Aims/Introduction

How to measure insulin resistance (IR) accurately and conveniently is a critical issue for both clinical practice and research. In the present study, we tried to modify the β‐cell function, insulin sensitivity, and glucose tolerance test (BIGTT) in patients with normal glucose tolerance (NGT) and abnormal glucose tolerance (AGT) by oral glucose tolerance test (OGTT) and metabolic syndrome (MetS) components.

Materials and Methods

There were 327 participants enrolled and divided into NGT or AGT. Data from 75% of the participants were used to build the models, and the remaining 25% were used for external validation. Steady‐state plasma glucose (SSPG) concentration derived from the insulin suppression test was regarded as the standard measurement for IR. Five models were built from multiple regression: model 1 (MetS model with sex, age and MetS components); model 2 (simple OGTT model with sex, age, plasma glucose, and insulin concentrations at 0 and 120 min during OGTT); model 3 (full OGTT model with sex, age, and plasma glucose and insulin concentrations at 0, 30, 60, 90, 120, and 180 min during OGTT); model 4 (simple combined model): model 1 and model 2; and model 5 (full model): model 1 and 3.

Results

In general, our models had higher r² compared with surrogates derived from OGTT, such as homeostasis model assessment‐insulin resistance and quantitative insulin sensitivity check index. Among them, model 5 had the highest r² (0.505 in NGT, 0.556 in AGT, respectively).

Conclusions

Our modified BIGTT models proved to be accurate and easy methods for estimating IR, and can be used in clinical practice and research.     

Inhibition of left ventricular stimulation due to left ventricular lead failure and the left ventricular T‐wave protection algorithm in patient with cardiac resynchronization therapy and pacemaker dependency

The electrocardiogram (ECG) interpretation in patients with cardiac resynchronization therapy (CRT) is often a perplexing problem. The difficulty in the device evaluation increases in the presence of unfamiliar timing cycles and a lead dysfunction. Authors describe a special function of a Biotronik CRT devices called the left ventricle T‐wave protection (LVTP), and demonstrate its behavior in a patient with left ventricular (LV) lead failure. This report shows that sometimes it might be difficult to understand the loss of resynchronization in 12‐lead ECG when LVTP feature is on, and a malfunction of left ventricular lead sensing occurs.     

Development and validation of a bi‐lingual interactive tool to educate people about osteomalacia

Osteomalacia is a condition where bone mineralisation is impaired by lack of vitamin D. It more commonly affects darker skinned individuals in the UK, especially if they wear occlusive clothing. Lifestyle changes and Vitamin D supplementation are recommended for those people most at risk through these factors, but such advice is not commonly followed. This indicates an educational need for information on osteomalacia and its treatment. Using a previously developed Mind‐Map on osteomalacia, a layered and interactive” PowerPoint” style presentation was developed, using hyperlinks. The “basic” layer was translated into Urdu and validated by Urdu speaking professionals. The translation was accurate and meaningful and the tool was well received by representatives of the community. The tool was used to educate a group of 10 community leaders from the Urdu community in Stourbridge, UK. Knowledge about osteomalacia was tested in these people, before and after the education, and increased from an average of 14 to 25 points (p < 0.05). Qualitative feedback gained was very positive. Conclusion: An interactive educational tool for Osteomalacia was developed and translated into Urdu. Use of the tool resulted in increased knowledge about osteomalacia.     

Triplane tissue Doppler imaging to evaluate mechanical dyssynchrony before and after cardiac resynchronization in a patient with congenitally corrected transposition of the great arteries

We report the case of a 13-year-old girl with congenitally corrected transposition of the great arteries. Since the implantation of a conventional pacemaker for acquired complete atrioventricular block, the patient experienced increased heart failure symptoms. Using triplane tissue Doppler imaging, significant intraventricular dyssynchrony induced by unilateral pacing and associated with diminished exercise capacity was demonstrated. A biventricular pacemaker was successfully implanted transvenously, leading to synchronous activation of the systemic ventricle and improved exercise capacity.     

Development of a carpark cardiac implantable electronic device clinic to improve time efficiency and patient satisfaction in the context of restrictions imposed by the COVID-19 pandemic

Introduction

We evaluated time efficiency and patient satisfaction of a “car park clinic” (CPC) compared to traditional face-to-face (F2F) during the COVID-19 pandemic.

Methods

Consecutive patients attending CPC between September 2020 and November 2021 were surveyed. CPC time was recorded by staff. F2F time was reported by patients and administrative data.

Results

A total of 591 patients attended the CPC. A total of 176 responses were collected for F2F clinic. Regarding satisfaction, 90% of CPC patients responded “happy” or “very happy.” 96% reported feeling “safe” or “very safe.” Patients spent significantly less time in CPC compared to F2F (17 ± 8 vs. 50 ± 24 min, p < .001).

Conclusion

CPC had excellent patient satisfaction and superior time efficiency compared to F2F.     

Benefit of cardiac resynchronization therapy to a patient with a narrow QRS complex and ventricular dyssynchrony identified by tissue synchronization imaging.

This report described an 81-year-old woman with severe symptomatic heart failure, reduced ejection fraction, mitral regurgitation, and an electrocardiographic QRS width of 118 ms who had ventricular dyssynchrony identified by echocardiographic tissue synchronization imaging. Because of her severe heart failure symptoms on maximal medical therapy, referral to implant a defibrillator, and mechanical dyssynchrony, she underwent cardiac resynchronization-defibrillator therapy with lateral left ventricular lead placement. This resulted in an immediate 30% increase in stroke volume and 35% decrease in mitral regurgitation. Echocardiographic tissue synchronization imaging may play a role in identifying mechanical dyssynchrony in patients with narrow QRS duration who may potentially benefit from cardiac resynchronization therapy.