Changes in left ventricular diastolic filling during the development of left ventricular hypertrophy: observations using Doppler echocardiography in a unique canine model

Sleep-disordered breathing and heart failure: focus on obstructive sleep apnea and treatment with continuous positive airway pressure

BACKGROUND

Among patients with heart failure, sleep-disordered breathing is a common problem, with a prevalence ranging from 24% to 76%. Encompassed within the general category of sleep-disordered breathing are 2 types of sleep apnea: obstructive sleep apnea (OSA) occurs when the oropharyngeal musculature relaxes, causing a collapse of the upper airway, and central sleep apnea occurs when the brain stem fails to stimulate breathing.

METHODS AND RESULTS

This article focuses on the relationship between heart failure and OSA, the treatment of OSA with continuous positive airway pressure (CPAP), and the role of CPAP in improving such effects of heart failure as ejection fraction, blood pressure, sympathetic activity, sleepiness, heart rate, and mortality.

CONCLUSIONS

It is important to distinguish the type of sleep-disordered breathing a patient may have. Further studies are needed to elucidate the effects of CPAP and other therapies.

Advances in echocardiography

Echocardiography is an exceptionally useful technique for diagnosing cardiovascular disease in small animals. It is noninvasive and provides a wealth of data concerning cardiac morphology and function. For many patients, echocardiography is the definitive diagnostic tool. A well-performed study coalesces the findings of the physical examination, electrocardiogram, and radiographs into a clearly defined diagnosis on which treatment decisions can be based. More so than other diagnostic techniques, echocardiography is highly operator dependent and relies on the proper acquisition and interpretation of results by an examiner who is familiar with the principles, capabilities, and limitations of ultrasound imaging. This article reviews the basics of echocardiography, measurement of cardiac dimensions, and assessment of cardiac function. Within these sections, emerging technologies that expand the capabilities of the echocardiographic examination are introduced.

Left ventricular diastolic dysfunction in patients with hypertension and preserved systolic function

OBJECTIVE

To assess prospectively diastolic function in hypertensive patients with preserved left ventricular function, particularly focusing on the limitation of the transmitral flow velocity curve alone to detect diastolic dysfunction.

PATIENTS AND METHODS

Comprehensive Doppler analysis was performed in 51 hypertensive patients with preserved left ventricular systolic function.

RESULTS

The ratio of the peak early diastolic filling wave velocity to the peak velocity of filling wave at atrial contraction was less than the age-adjusted mean value minus 2 SD in 16 patients, and the other 35 patients had a "normal" transmitral Doppler signal. However, the combined transmitral and pulmonary venous Doppler analysis revealed that 12 of these 35 patients had a "pseudonormal" pattern. The prevalence of diastolic dysfunction was estimated at 31% with use of transmitral Doppler alone but increased to 55% when comprehensive Doppler analysis was used (P < .05).

CONCLUSION

The presence of diastolic dysfunction has been frequently overlooked in hypertensive patients with transmitral Doppler analysis alone, and an assessment of diastolic function with a comprehensive Doppler analysis is needed in patients at risk for diastolic dysfunction.

Doppler echocardiography. I. Pulsed-wave and continuous-wave examinations

Doppler echocardiography is a specialized processing of cardiac ultrasound that is characterized by a continuously updated display of blood velocity during the cardiac cycle. Doppler examinations, which include color-coded Doppler echocardiography, pulsed-wave examination, and continuous-wave studies, are readily applicable to veterinary patients.

Left Ventricular Diastolic Function

Two-dimensional echocafdiography has gained widespread acceptance I as the procedure of choice to evaluate left ventricular function. In the last decade, the importance of diastolic function in the overall performance of the left ventricle has received much attention. Recent evidence suggests that diastolic dysfunction may contribute to symptoms of left heart failure in many patients, including those with normal sys tolic function. Alterations in transmitral Dop pler flow velocity patterns have been used to assess changes in left ventricular diastolic func tion. This article reviews the concept and clin ical signincance of diastolic function and the assessment of diastolic function by Doppler echocardiography.

Obstructive sleep apnea and blood pressure elevation: what is the relationship? Working Group on OSA and Hypertension

Sleep disordered breathing has increasingly been recognised as a frequent cause of ill-health in the community. Moderate or severe forms of the most common condition, obstructive sleep apnea (OSA), occur in up to 12% of the adult male population. A substantial body of literature has been published on the potential relationship between OSA and cardiovascular disease. In particular, OSA has been associated with cardiac failure, stroke, myocardial infarction and hypertension. Part of this association may be explained by other confounders, mainly obesity, which is common in OSA patients. The present review was prepared following a workshop aimed to critically review available scientific evidence suggesting that hypertension is a direct consequence of OSA. In addition, pathophysiologic mechanisms that may be involved in the relationship between OSA and cardiovascular disease, particularly brief intermittent elevation of blood pressure and sustained systemic hypertension, are discussed.