Influence of amyl nitrite inhalation on the systolic time intervals in normal subjects and in patients with ischemic heart disease

Factors associated with high brachial-ankle pulse wave velocity in non-hypertensive and appropriately treated hypertensive patients with atherosclerotic risk factors

While pulse wave velocity (PWV) correlates with blood pressure (BP), its extent differs between patients, and some cases of high PWV in normotensives are present. Moreover, PWV frequently remains high in hypertensive patients despite adequate BP control. The factors associated with such phenomena are yet to be elucidated. Here, we investigated the factors associated with brachial–ankle PWV (baPWV) in 107 patients whose systolic BP was under 140 mmHg at their latest baPWV measurement. There were 64 controlled hypertensives and 43 normotensives. Multivariate regression analysis identified age, hypertension, body mass index (BMI), systolic BP, and heart rate (HR) as independent factors for baPWV. Next, we divided the subjects into groups according to their age (in 5-year increments) and calculated the mean and standard deviation (SD) of the baPWV for each group. For each age group, we defined patients with a baPWV above the mean + SD baPWV for the group as the high-baPWV cohort. Multivariate logistic regression analysis revealed that BMI, hypertension, and smoking were independent determinants of a high-baPWV subject. This represents the first study to report the existence of the hypertensive state itself as one of the independent predictors of high baPWV in normotensive and well-treated hypertensive patients. This finding implies that the hypertensive state itself possibly worsens arterial stiffness independently from aging in spite of adequate BP maintenance. To prevent the early progression of arterial stiffness, the application of an appropriate intervention during the early stages of hypertension is important and the continuation of an appropriate BP treatment is suggested.

Evaluation of the pulse wave arrival time as a marker for blood pressure changes in critically ill infants and children

OBJECTIVE

Pulse arrival time (PAT), which is the interval between the R wave of the electrocardiogram (ECG) and the arrival of the pulse wave peripherally, has been reported to be suitable for use as an indirect measure of blood pressure change. The purpose of this study was to evaluate, in critically ill infants and children, the degree to which 1/PAT covaries with systolic, diastolic, and mean blood pressure, as well as heart rate.

METHODS

A laboratory device was used to calculate PAT in real time from the ECG and the plethysmographic curve of pulse oximetry used for routine monitoring. Calculated PAT and corresponding blood pressures and heart rate were stored on hard disk. A total of 15 critically ill patients, aged 6 days to 16 years, weighing 3 to 80 kg, were studied.

RESULTS

In all patients, one period of 11,000 to 36,000 beats could be evaluated. Mean correlation coefficients were best for systolic blood pressure (r = 0.73), followed by mean blood pressure (r = 0.68) and diastolic blood pressure (r = 0.61), and, finally, heart rate (r = 0.52). In 7 patients, the correlation coefficient for systolic blood pressure was > 0.9; but, in 4 patients, it was < 0.5.

CONCLUSIONS

We conclude that the correlation between 1/PAT and systolic blood pressure is not strong enough to serve as a marker for blood pressure changes in critically ill infants and children. This may be due to changes of the preejection period, which is part of the PAT.

Cardiac consequences of diabetes mellitus

A variety of disciplines including noninvasive and invasive cardiac methodologies, as well as epidemiologic studies, have provided information that has altered our view on the relation of diabetes to cardiac disease. Instead of an exclusive focus on coronary artery disease, it is now recognized that heart muscle can be independently involved in diabetic patients. In diabetics without known cardiac disease, abnormalities of left ventricular mechanical function have been demonstrated in 40 to 50% of subjects, and it is primarily a diastolic phenomenon. Left ventricular hypertrophy may eventually appear in the absence of hypertension. The diastolic dysfunction appears related to interstitial collagen deposition, largely attributable to diminished degradation. The presence of even moderate obesity intensifies the abnormality. Reversibility of this process is not readily achieved with chronic insulin therapy. Experimental studies have indicated normalization of the collagen alteration by endurance training, begun relatively early in the disease process. General measures of management include the control of other cardiac risk factors and a reasonable program of physical activity. The high mortality during an initial acute myocardial infarction has been attributed to heart failure, which is managed as in nondiabetic patients. Recently, the early introduction of aspirin, thrombolysis, and beta-adrenergic blockade has reduced mortality during the initial infarction. Chronic use of the latter agent over the subsequent years has also proven to be more beneficial in diabetic patients with acute myocardial infarction compared with nondiabetic patients.

Subtle features of the hemodynamic response to amyl nitrite inhalation: new aspects of an old tool

Although amyl nitrite inhalation (ANI) antedates all current short acting vasodilators as a clinically useful pharmacologic stressor, few clinicians are aware of the subtle hemodynamic actions of this agent. This study examined transients in left and right heart hemodynamics after ANI in seven men (ages 44 +/- 7 years) undergoing elective cardiac catheterization. High-fidelity central aortic (AoP), left ventricular (LVP), pulmonary artery (PAP), right ventricular (RVP), and right atrial (RAP) pressures were simultaneously recorded from left and right heart multisensor catheters. As expected, ANI caused an acute fall in Ao pressure (27%; p < 0.01) and reflex tachycardia (p < 0.001). Little change was noted in PAP, RVP, RAP, or LV end-diastolic pressures or the time constant of LV isovolumetric relaxation (tau). LV ejection time decreased 23 +/- 10 ms (p < 0.05) and RV ejection time did not change. Baroreflex sensitivity was similar during pressure fall and recovery (6.4 +/- 4.5 vs. 6.1 +/- 3.6 ms/mmHg), however hysteresis (p < 0.05) was noted. Aortic pressure waveforms also changed following ANI. Changes were determined to be in part a consequence of the attenuation and delay in arterial wave reflections. This study extends the understanding of the complex nature of the hemodynamic response associated with ANI.

The effect of verapamil on cardiac sympathetic function

We have used systolic time intervals (STI) to measure inotrophy and chronotropy as indirect measures of the actions of noradrenaline, in order to ascertain whether the depletion of cardiac noradrenaline stores which has been shown to occur in laboratory rats after chronic verapamil treatment could be demonstrated in healthy volunteers. Placebo, verapamil, or atenolol were given by slow intravenous injection to 8 healthy volunteers and QS2I, LVETI, and PEP/LVET were measured. Verapamil pretreatment resulted in a positive inotropic state. Intravenous verapamil after oral pretreatment caused accentuated negative inotropic and chronotropic responses as compared with acute verapamil without pretreatment. We postulate that the observed initial inotropic effect may be in part due to an increase in the amount of noradrenaline available to the myocardium intrasynaptically, and that the accentuated negative response after intravenous or oral verapamil may result from a decrease in cardiac noradrenaline storage.

Asymptomatic myocardial infarction in Kawasaki disease: long-term prognosis

Eight patients with Kawasaki disease who had sustained asymptomatic myocardial infarction 8-15 years ago (mean, 13.1 years) were reexamined by various noninvasive cardiac function tests to assess long-term prognosis. At present, electrocardiograms (ECGs) are normal in six patients. However, all eight patients had a prolonged preejection period (PEP) to left ventricular ejection time (LVET) ratio 30 s after amylnitrate (AN) inhalation. Six patients had perfusion defects by exercise thallium-201 myocardial scintigraphy, and two patients developed ST segment depression in treadmill exercise testing. These patients are symptom-free even though their physical activity has not been restricted. Yet they proved to have serious abnormalities suggesting sequelae of myocardial infarction or existing myocardial ischemia. Judging from the results of noninvasive cardiac function tests and recently performed coronary angiography, five of the eight patients require coronary bypass surgery.

Significant coronary artery disease detected by amyl nitrite and systolic time intervals

The relation between changes in left ventricular systolic time intervals with amyl nitrite (AN) inhalation and the severity of coronary artery disease (CAD) was evaluated in 77 patients who underwent catheterization because of chest pain. In 25 subjects with normal coronary angiograms (control group), AN inhalation increased the ejection time (ET), shortened the preejection period (PEP) and increased the ET/PEP markedly. In the 52 patients with CAD (CAD group), the ET/PEP changed insignificantly after AN. The difference between the 2 groups was significant (p less than 0.001). At cardiac catheterization, the increase of left ventricular dP/dt after AN in the control group was significantly larger than that in the CAD group. Although a positive correlation between changes in ET/PEP with AN and ejection fraction at rest was noted in patients with 1-vessel CAD, no such correlation was noted in those with multivessel CAD. This suggests that factors in addition to pump function, such as the degree of CAD, influence the effect of AN inhalation on systolic time intervals. When an increase of less than 30% in ET/PEP occurs with AN inhalation, the presence of significant CAD can be detected with a sensitivity of 92%, a specificity of 84% and the predictive value of 92%. The AN inhalation test is safe and simple, and thus could serve as a stress test for evaluating the presence and severity of significant CAD.

Systolic time intervals: a review of the method in the non-invasive investigation of cardiac function in health, disease and clinical pharmacology

Measurement of systolic time intervals is a valuable, non-invasive procedure to assess left ventricular performance, particularly when influenced by drugs. In this review, we discuss various factors affecting systolic time intervals, the therapeutic implications of the technique and its place among other non-invasive tests of cardiac function.

Acute haemodynamic effects of a new calcium antagonist, nicardipine, in man. A comparison with nifedipine

1 The acute cardiovascular response to nicardipine was investigated using non invasive techniques in normal subjects. 2 In six subjects, i.v. nicardipine in an increasing dose (0.5-20 mg) was compared with saline, under double-blind conditions. A dose related increase in heart rate and fall in blood pressure were found. Pre-ejection period (PEP) and PEP/left ventricular ejection time (LVET) ratio of the systolic time intervals were shortened in a clearly dose related manner. Total electromechanical systole index (QS2 I) was decreased and LVET index prolonged. 3 In four subjects increasing oral doses (10-40 mg) of nicardipine, administered in a randomized double-blind placebo control design, demonstrated the same pattern, marked changes being found with the 40 mg dose. 4 Comparison with nifedipine in a double-blind-placebo controlled balanced trial in six subjects confirmed that 40 mg nicardipine and 20 mg nifedipine exhibited similar effects. Maximum response was reached between 0.5 and 1.5 h, and changes in some cardiovascular variables were still evident at 3 h.

Effects of amyl nitrite on left ventricular relaxation in patients with borderline hypertension

The effects of systemic hypertension on left ventricular relaxation properties remain largely undefined. To assess such effects 22 normal volunteers and 15 patients with borderline hypertension were examined. The tangent to the echocardiographic left ventricular posterior wall endocardium was measured in diastole and was normalized for end-diastolic dimension to yield normalized velocity of relaxation. This velocity of relaxation was measured at rest and throughout inhalation of amyl nitrite. Mean value +/- standard deviation (SD) from rest to peak amyl nitrite effect for the normal group and for the patients with borderline hypertension was 3.3 +/- 0.6 leads to 7.2 +/- 1.1 and 3.0 +/- 0.8 leads to 4.4 +/- 1.1 s-1, respectively. All 22 persons in the normal group and 2 of the 15 patients with borderline hypertension attained normalized velocity of relaxation greater than 5.5 s-1 with administration of amyl nitrite. Multivariate analysis in the normal group identified heart rate, mean arterial pressure, and fractional shortening as the best predictors of normalized left ventricular relaxation velocity (r = 0.85; p less than 0.001). The increase in the normalized velocity of relaxation induced by amyl nitrite is blunted in patients with borderline hypertension. These changes in left ventricular relaxation identify early cardiac involvement and may prove clinically useful in hypertensive patients.

Effect of isocapnic hypoxia on systolic time intervals in conscious man

The effects of progressive isocapnic hypoxia on the systolic time intervals were studied in 10 healthy human subjects. We induced hypoxia by a rebreathing method and monitored the arterial oxygen saturation continuously and non-invasively by means of an ear oximeter. Arterial oxygen saturation (SaO2) was allowed to fall to a level of 75 per cent and was then held constant for five minutes. As SaO2 fell, heart rate increased linearly, with a mean increase of 0.83 beats/min per one per cent fall in SaO2. The pre-ejection phase index decreased from a mean of 127.2 ms at full oxygen saturation to 120.1 ms at steady-state hypoxia levels, while the ratio of the pre-ejection phase to left ventricular ejection time decreased from a mean of 0.330 to 0.301. The left ventricular ejection time index increased from 417.4 ms to 429.3 ms, while no statistically significant difference was found in the length of electromechanical systole.

Left ventricular performance in diabetic patients without clinical heart disease. Evaluation by systolic time intervals and echocardiography

To examine left ventricular performance in diabetic patients without clinical evidence of cardiac involvement, systolic time intervals (pre-ejection period, left ventricular ejection time index and ratio of pre-ejection period to left ventricular ejection time) and echocardiographic measures (percentage changes in minor axis diameter, end-diastolic and end-systolic diameter, end- diastolic volume and end-systolic volumes, stroke volume and ejection fraction), were obtained. There were 89 diabetic patients and 93 control subjects evaluated for systolic time intervals, and 40 diabetic patients and 20 control subjects evaluated by echocardiogram. The diabetic group demonstrated significant (P less than 0.001) differences from the normal control group in each of the noninvasive measures of systolic time intervals. Pre-ejection period/left ventricular ejection time ration was increased by 25 percent and the pre-ejection period was increased by 12 percent in the diabetic patients. Among 40 diabetic patients studied by echocardiography, abnormal percentage change in minor axis diameter, (less than 30 percent) occurred in six individuals. Ejection fraction was decreased by 20 percent as compared to the control group, whereas end-diastolic pressure was not significantly different in the groups.

A critical review of the systolic time intervals

The theoretical basis for the use of the systolic time intervals has been largely established. The method has been validated by direct measures from within the circulatory system. Standards for equipment and technique have been defined. Numerous clinical studies have demonstrated the value of this quantitative noninvasive technique for assessing left ventricular performance. At present there is need for further studies of the clinical usefulness of the systolic time intervals to improve both diagnosis and therapy of various cardiovascular disorders.

Effect of certain antiadrenergic agents on systolic time intervals in essential hypertension

Systolic time intervals, including preejection period (PEP) and left ventricular ejection time (LVET), were studied in patients with permanent essential hypertension before and after intra-venous administration of propranolol 0.2 mg/kg (11 patients), clonidine 0.002 mg/kg (10 patients) and methyldopa 2 mg/kg (12 patients). With propranolol, diastolic blood pressure was unchanged and the heart rate decreased, whilst PEP and LVET were significantly prolonged (P less than 0.001). Clonidine caused a fall in blood pressure (P less than 0.001), heart rate was slightly reduced, PEP was prolonged (P less than 0.001) and there was a significant decrease in LVET at 5 min. With methyldopa, no significant effect was observed after intravenous injection, but 7 days oral administration produced the identical effect as clonidine. These observations suggest that certain antihypertensive drugs may impair left ventricular performance and depress myocardial contractility.

The effect of quinidine sulfate on QRS duration and QT and systolic time intervals in man

QRS duration, QT interval, total electromechanical systole (QS(2)), left ventricular ejection time (LVET), and preejection period (PEP) were determined in five male and two female healthy volunteers in a fasting state at hourly intervals for 7 hours during a control period and after administration of 400 mg quinidine sulfate. Changes of QRS duration (delta QRS) and rate-corrected QT interval (delta QTc) were calculated before and after quinidine. Deviations of measured QS(2), LVET, and PEP from the normal were calculated as the differences between the observed interval and those predicted from the normal regression equation. The effect of quinidine on systolic time intervals (delta QS(2), delta LVET, DELTA PEP) were expressed as the differences between the deviations from the normal regression equation during the control period and after the drug administration. After quinidine sulfate delta QRS, delta LVET, delta PEP, and delta PEP, delta LVET were slight and inconsistent. However, delta QTc and delta QS(2) were significant (at P is less than 0.05 or better) from the first hour to the 7th hour and from the 2nd hour to the 5th hour, respectively. The mean maximum delta QTc was 44.8 milliseconds and delta QS(2) was 29.9 milliseconds. The significant changes of QTc and QS(2) seemed to occur at the plasma level range of 0.75-1.9 mug/ml. This study indicates that of the various systolic time interval measurements obtained after quinidine administration, the changes of QT interval and QS(2) are most significant and that these changes seem to occur even at low plasma levels.

Hemodynamic changes associated with angina pectoris induced by maximal treadmill exercise: effect of sublingual isosorbide dinitrate on systolic time intervals

A technique for the study of patients with angina pectoris has been described, in which systolic time interval (STI) measurements are obtained at intervals after the onset of stress-induced angina. The technique is uniquely suited to the evaluation of anti-anginal drugs. Sublingual isosorbide dinitrate (SISD) was randomly alternated with a placebo (P) tablet in a double-blind study of 20 patients with stable angina pectoris. After SISD, compared to placebo, a highly significant shortening of Q-S2 and LVET occurred (p less than 0.001) which lasted throughout the entire 120 minute study period. The hemodynamic basis for these differences was felt to be improved myocardial contractility secondary to a reduction in systemic vascular resistance and reduced venous return induced by the SISD. A significant prolongation of PEP occurred at 60 minutes post-SISD (p less than 0.01). This was attributed to an increase in the gradient between LVEDP and aortic diastolic pressure resulting from reduced venous return after SISD. The PEP/LVET ratio was significantly increased up to 60 minutes after SISD (P less than 0.05). Heart rate was uniformly higher post-SISD, compared to post-placebo values; the differences were highly significant up to 60 minutes (P less than 0.001) and remained significant at 120 minutes (p less than 0.05). The time to angina was significantly longer (immediately post SISD, p less than 0.05; 30 min, p less than 0.001; 60 mins, p less than 0.05; 120 mins, p less than 0.05); and the work load greater, for 120 minutes following SISD: the increase in the latter was highly significant for 30 minutes after SISD (p less than 0.001) and remained significant up to 120 minutes (60 mins, p less than 0.05; 120 mins, p less than 0.05). These observations were attributed to an improvement in myocardial function due to the sublingual isosorbide dinitrate. A high degree of correlation was found to exist between heart rate and the STI. This correlation was negative for the QS2 interval (-0.996) and LVET (-0.993) and positive for PEP (+0.817) and the PEP/LVET ratio (+0.950).

Polygraphic studies of the effect of nitroglycerin in patients with ischaemic heart disease

Images

Duration of phases of left ventricular systole using indirect methods. I. Normal subjects

Images