Blood Pressure Measurements in 780 Apparently Healthy Cats

Table of Contents

Materials and Methods

This study was approved by the Royal Veterinary College ethics and welfare committee (Unique Reference Number 2010 1004).

The cats enrolled in this study originally were enrolled as part of a study of apparently healthy cats to assess the prevalence of heart murmurs on auscultation and myocardial disease on echocardiography, and the methods for this study have been described previously.20 In brief, cats from 2 rehoming centers in the South East of the United Kingdom¹ were included in a cross‐sectional study (the “CatScan” study). All cats aged 6 months or older that were available for rehoming were enrolled, provided they were considered healthy based on known history and routine physical examination as performed by the veterinary staff at the rehoming center. Cats were excluded if they were hypertensive (SBP ≥180 mmHg); if they were receiving any medical treatment reported to affect blood pressure; if they were hyperthyroid or on medical management for hyperthyroidism; if they had systemic disease causing clinical signs (e.g, cats with azotemia identified on routine screening blood testings were included as long as the cats were not polyuric or polydipsic); or if they were pregnant or nursing queens. Cats were not excluded if they had a murmur auscultated or if they had echocardiographic evidence of cardiac disease. Serum biochemistry and total thyroxine concentrations only were measured if the rehoming center staff thought it to be clinically necessary on the basis of known history or physical examination.

Data collected included age (often as an estimated age range), date of birth (if known), sex, neuter status (if known), breed (based on appearance rather than using pedigrees), and whether the cat was a stray or had been relinquished to the home by a previous owner. Cats then were assessed as to their temperament, with cats rejected at this stage if they were deemed aggressive or too nervous to be handled. Cats that were initially classified as too aggressive or too nervous to handle such that it was impossible to measure blood pressure could be reassessed at a later date. These cats were included if they were no longer too aggressive or nervous to be handled at the subsequent examination.

While cats were habituating to the examination room, their medical records were assessed and any concurrent or historical medical problems were recorded, as was the date of neutering, if known. Cats would be habituated for at least 5 minutes routinely, and for up to 20 minutes if the cat appeared anxious. Once settled, cats were weighed and their body condition score (BCS) was assessed on a scale of 1–9 based on the Purina scale.21 Cats underwent indirect systolic blood pressure (SBP) measurement, performed as recommended by the ACVIM Consensus Statement1 using a Parks Doppler unit² in a quiet room. All measurements were performed by a single observer (JRP) who had 3 years of experience using Doppler sphygmomanometry. Blood pressure cuff size was selected so that the cuff width was 30–40% of the circumference of the limb at the cuff site. Cats were allowed to settle into a position of their choosing once the cuff had been attached. For convenience, the default limb used was the right forelimb and this was only altered if that limb was missing or injured, if the cat resented the right forelimb being touched, or if variable or unexpectedly low or high results were generated from the right forelimb. If the right forelimb was not used, the left forelimb was used. After at least 30 seconds of acclimatization (time dependent on the level of nervousness of the cat), the sphygmomanometer was attached, the hair over the artery was moistened with ultrasound gel, and the probe was placed over the region of the first palmar common digital artery. Hair was not removed in any cat for the purposes of blood pressure assessment. Again, a small period of acclimatization was allowed before the machine was turned on, the strongest signal located, and measurements were made. Throughout the assessment, the cuff was kept as level as possible with the level of the right atrium. For cats in lateral recumbency, the sternum was used as an estimate of the right atrial level. For cats that were sitting or were in sternal recumbency, a point 40% up an imaginary line from the sternum to the dorsal spinous processes at the level of the caudal border of the scapula was used as an estimate of the right atrium. At least 6 measurements were recorded, with the first measurement being automatically discarded and any discordant results also being excluded. If discordant results were obtained, additional measurements were taken until there were 5 similar values to average. In addition to recording the cuff size and site, the position of the cat was recorded (standing, sitting, lying in sternal recumbency, lying in left lateral recumbency, or lying in right lateral recumbency) as was the cat’s demeanor22 during the blood pressure assessment (Table 1). Cats may have been considered aggressive during assessment of SBP but not excluded from the overall study if the aggression was not sustained and did not result in injury to the people involved.

At the completion of the study, medical records kept by the rehoming center were reassessed to make sure that no cat had been subsequently diagnosed with a condition that would exclude it from the project after its screening.